AlllOS 6^6335

NBS

PUBLICATIONS

vJ .. ifc NBSIR 81-2311

Analysis of Results of IVlini

Round Robin Reflectance Test

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

Thermal Processes Division

National Engineering Laboratory

Center for Chemical Engineering

* Washington, DC 2C234

August 1981

100

.Obb

81-2311 /

1981

C.2

U.S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU Of STANDARDS

NBSIR 81-2311

ANALYSIS OF RESULTS OF MINI

ROUND ROBIN REFLECTANCE TEST

OF flTANPARl>o libbabt

SEP i6 w

, 'J

' --

J/n/

rf- . :

J. C. Richmond

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

Thermal Processes Division

National Engineering Laboratory

Center for Chemical Engineering

Washington, DC 20234

August 1 981

U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige, Secretary

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director

CONTENTS

Page

LIST OF TABLES iv

LIST OF FIGURES v

INTRODUCTION 1

PARTICIPATING LABORATORIES _ 1

PRELIMINARY DISUCSSION 1

SAMPLES FOR MEASUREMENT 3

DATA REQUESTED 3

RESULTS OF MEASUREMENTS 3

APPENDIX I 7

MEASUREMENT PROCEDURE 8

ill
LIST OF TABLES

Table 1

Table 2

Table 3

Table 4

Table 5

Results of Round Robin Test on VTiite Samples

B.esults of F.ound Robin Test on Black Samples

Reported Values for Solar Properties

Procedures Used for Computing Solar Properties

Differences as Fraction of Reported Solar Values

iv
f

I LIST OF FIGURES

Figure 1 - Difference between the data reported by Laboratory 1

and calibration data for the white sample, plotted as a function of wavelength.

il Figure 2 - Difference between data reported by Laboratory 2 and calibration

j data for the white sample, plotted as a function of wavelength.

I

:

!|i| Figure 3 - Difference between data reported by Laboratory 3 and calibration

1 data for the white sample, plotted as a function of wavelength.

11!

Figure ^ - Difference between data reported by Laboratory 4 and calibration

data for the black sample, plotted as a function of wavelength.

Figure 5 - Difference between the data reported by Laboratory 1

^ and the calibration data for the black sample, plotted as a

j function of wavelength.

Figure 6 Difference between the data reported by Laboratory 2 and calibration

data for the black sample, plotted as a function of wavelength.

Figure 7 - Difference between the data reported bv Laboratory 3 and the

calibration data for the black sample, plotted as a function

of wavelength.

Figure 8 - Difference between data reported by Laboratory 4 and the

calibration data for the balck sample, plotted as a function

of wavelength.

V

-1-

Introduction

A round-robin test of directional-hemispherical reflectance measurements

was conducted by the National Bureau of Standards at the request of the

Solar Energy Research Institute. Four national laboratories participated.

Measurements were made of the directional-hemispherical reflectance of

two samples, having high and low reflectance, respectively, in the

wavelength range of 250 to 2500 nm.

Measured directional-hemispherical reflectance is used to compute

solar reflectance of materials, and solar absorptance of opaque materials.

The overall objective of the round-robin test was to obtain data on the

performance of the several laboratories in making such measurements.

Since all participants were national laboratories, it is to be expected

that the accuracy of such measurements will approach the state of the

art for measurements made with commercially available instruments.

Participating Laboratories

The participating laboratories, in alphabetical order are:

1. Battelle Pacific Northwest Laboratories, Richland, Washington

2. National Bureau of Standards, Center for Building Technology,

National Engineering Laboratory, Gaithersburg, Maryland

(Mail address: Washington, D.C.)

3. Sandia National Laboratory, Albuquerque, New Mexico

4. Solar Energy Research Institute, Golden, Colorado

In addition to the above, the reference measurements on the samples

to which the reported values were compared, were made in the Radiometric

Physics Division of the Center for Radiation Research, National Measurement

Laboratory of NBS. The high-accuracy ref lactometer designed and built

at NBS was used for these measurements.

Preliminary Discussion

An integrating sphere ref lactometer , the instrument used in evaluating

directional-hemispherical reflectance, actually measures directionalnear-hemispherical reflectance factor. Reflectance is defined as the

ratio of reflected flux to incident flux. Reflectance factor is defined

as the ratio of the flux reflected by a sample under specified conditions

of irradiation and viewing, to that reflected by the ideal completely

reflecting, isotropically diffusing surface. Such an ideal surface does

not exist, but it is closely approximated by several materials which are near-perfect isotropic diffusers, and have high reflectance. If the

reflectance of such a material is known, a correction can be made for

its reflectance.
-2 -

It is physically impossible to design an instrument that has true

directional irradiance and hemispherical collection, because the solid

angles of irradiance and collection are mutually exclusive. Some of the

reflected flux is lost out the entrance aperture of the sphere, and some

is lost out the detector aperture. The fraction of the flux lost in

this manner is approximately equal to the ratio of the total area of all

apertures to the total area of the sphere wall, apertures included. If

the diameter of the apertures is small compared to the diameter of the

sphere, the fractional losses will be small.

In a reflectance factor measurement in which a comparison standard

of known reflectance is used, the flux losses through the ports will be

exactly compensated for if the relative geometric (directional) distribution of the reflected flux is the same for sample and standard. If

both sample and standard reflect diffusely, the losses will be nearly

compensated

For true geometrical conditions of hemispherical collection, reflectance

factor is identically equal to reflectance. For diffusely reflecting

samples, the measured directional-hemispherical reflectance factor will

be identically equal to the directional-hemispherical reflectance if

the ideal comparison standard is used, and the error will be small if a real diffusely reflecting standard is used and a correction is made for

the absolute reflectance of the standard.

Measurement of the absolute reflectance of a diffusely reflecting

sample is difficult and time-consuming. It is normally done only by a primary standards laboratory, and then only at rather long intervals.

An integrating sphere ref lectometer measures only the ratio of the

reflectance factor of a sample to that of the comparison standard used

in the measurement. The measured value will include uncertainties due

to (1) the error, if any, in the reflectance value assigned to the

comparison standard, (2) differences in the fractional flux losses out

the ports, due to differences in the geometrical distributions of

by the sample and reference, (3) nonlinearity of the detector-amplifier

system, and (4) scattering in double-beam instruments, so that some of

the flux in the reference beam is scattered into the sample beam, or^

vice versa. To this must be added an uncertainty due to the statistical

fluctuation in the output of the instrum.ent, usually referred to as noise.

With double-beam instruments, it is customary to run a 100% curve

and a zero curve. The 100% curve is obtained with identical samples in

the two beams. The zero curve is usually obtained when the sample beam

is blocked before entering the sphere. A correction for deviation of

the two curves from 100% and 0% respectively is made by use of the

following equation.

R

X Hx-0

X

X

( 1 )
-3-

where R, is the corrected directional-hemispherical reflectance factor,

) curve reading, and H, is the

The results of a round-robin test can be analyzed to give an estimate

of the fractions of the total error that may be due to bias and random

error, respectively, and may give some indication of the source of some

of the bias.

The samples sent to the participants were black and white samples,

either 50.8x50'. 8 mm (2x2 inch) or 25.4x25.4 mm (1x1 inch) for the black,

and 50.8x50.8 mm (2x2 inch) or 25.4x76.2 ram (l-l/2x3 inch) for the

white. The smaller samples were intended for measurement in instruments

utilizing an Edwards-type integrating sphere in which the sample is held

at the center of the sphere by a rod inserted through an aperture in the

top of the sphere. The aperture in these spheres is too small to admit

a 50.8x50.8 mm (2x2 inch) sample. The black samples were of black

porcelain enamel, with spectral directional-hemispherical reflectance in

the range of about 0.06 to 0.11 in the wavelength range of 250 to 2500

nm. The white samples were white ceramic tile, with reflectance generally

above 0.8 at wavelengths from about 500 to 2500 nm, dropping from about 0.8

at 500 nm to about 0.15 at 250 nm .

These samples were among those calibrated for directional-hemispherical

reflectance in the Radiometric Physics Division of NBS

The data requested from all participants was the measured directionalhemispherical reflectance for near-normal incidence, including the

specular component, and if possible, the same data for angles of incidence

of 15, 30, 45 and 60 degrees from normal. Data were requested at 10 nm

intervals over as much of the wavelength range of 250 to 2500 nm as the

measurement instrument was capable of providing. The instructions for

the test are given in Appendix 1.

The results reported by the different laboratories are shown in

Table 1 for the white samples and Table 2 for the black samples, together

with the calibration values for the sample measured in each case.

The values reported for the solar reflectance of the white sample

and the solar absorptance of the black sample are given in Table 3. The

procedures used to compute the solar properties are given in Table 4.

Because different samples were measured by each laboratory, direct

comparison of the reported values is not justified. The calibration

values for each sample at each wavelength are included in Table 1 in the

column headed "Cal", and the algebraic difference between the calibration

value and the reported value is included in the column headed "Diff".

X

Samples for Measurement

Data Requested

Results of Measurements
-4-

The difference values obtained by subtracting the calibration value

from the reported value were plotted as a function of wavelength as shown in figures 1 to 3. The average differences for the white samples

were about 0.029 for Lab 1, 0.012 for Lab 2, 0.019 for Lab 3 and 0.010

for Lab 4. The standard deviations associated with these values were

about 0.02 for Lab 1, 0.01 for Lab 2, 0.012 for Lab 3 and 0.003 for Lab

4 .

A review of figures 1 to 4, where the data for the white samples

are plotted, gives some clue_s to the errors that may be present in the

reported values. Figure 1 shows that the data are slightly wavelength

dependent. The average value of the difference is about 0.003, and the

standard deviation about 0.006. The wavelength dependence and average

'^iffsrsrice suggests that the values assigned to the halon reference are

in error, particularly at wavelengths below 600 nm.

Figure 2, showing the differences for Lab 2, indicates that the

values assigned to the Halon reference are high at wavelengths below

about 360 nm, and uniformly low by about .0013 at wavelengths beyond

about 400 nm.

Figure 3, showing the differences for Lab 3, indicates that the

errors are unacceptably high at wavelengths of 800 to 850 nm and at 1380

nm, and at the very short wavelengths in the ultraviolet and at wavelengths

beyond 1900 nm in the infrared. The peaks at about 820 nm and 1380 nm may be at the points where detectors were changed, and the signal-tpnoise ratio is small. The signal-to-noise ratio may also be small at

the two ends of the spectral range. The comparison standard used for

the measurements was not identified.

Figure 4, showing the differences for Lab 4, indicates that the

value assigned to the pressed Halon comparison standard may be low by

about 0.01. The random error is the lowest of any of the laboratories.

The average differences for the black samples are about 0.0056 for

Lab 1, 0.002 for Lab 2, 0.004 for Lab 3 and -.005 for Lab 4, and the

standard deviations are about 0.0013 for Lab 1, 0.0028 for Lab 2, 0.0043

for Lab 3 and 0.0037 for Lab 4.

Figure 5 is a plot of the differences for Lab 1 and shows an average

difference of 0.0056, and the standard deviation is about 0.0013. The

standard deviation is the lowest reported for the black samples, and

indicates a very low random error. There is a slight tendency for the

error to be greater at the short and long wavelengths. The bias in the

data, of about 0.5%, is much too large to be accounted for by an incorrect

value for comparison standard, since the value assigned to the comparison

standard would have to be about 8% high to account for such a large bias,

and the data on the white sample indicates that such a large error is

highly unlikely. The bias must be due to a zero line error. The equation

used for reducing the data as reported by the investigator, does not show

that a zero line correction was made.
-5-

Figure 6 shows that the bias in the results reported by Lab 2 is

very low, which is also indicated by the average difference of 0.00178,

the lowest reported by any of the laboratories for the black satrroles.

The standard deviation is about double that reported by Lab 1. There is no marked variation of the differences with wavelength.

Figure 7 shows that there is an overall trend of increasing difference

with wavelength. The peak at about 800 to 850 nm, which is very prominent

in figure 3, is still present, but the peak at about 1380 nm, if present,

is masked by the random error, which is the largest reported for a black

sample, as indicated by the standard deviation of about 0.004.

Figure 8 shows a slight trend toward increasing difference with

wavelength. There is a very pronounced peak at about 000 nm and valley

at about 1000 nm. This is near the wavelength where detectors are likely to be changed, and may be due to nonlinearity of the detectors in

spectral regions where the response is low. The random error appears to

be low, and the high standard deviation, 0.00433, appears to be due

largely to fluctuations of the difference with wavelength. Again, it

appears likely that the observed differences are due to zero line errors.

The coefficient of variation, the ratio of the standard deviation

to the mean, may be a more useful measure of the significance of the

errors in the measured reflectances. These are sho\^m in Table 5, in

which the mean reflectance is taken-as the solar reflectance reported by

each laboratory. The values for the white samples range from 0,0038 +

0.0069 for Lab 1 to 0.0225 + 0.0140 for Lab 3, and for the black samples

from 0.0250 + 0.0399 for Lab 2 to -.0811 + .0524 for Lab 1. The average

of the absolute values is 0.0128 + .00915 for the white samples, and

0.0456 + 0.0432. In each case the + uncertainty is taken as one standard

deviation. This is probably much too large for the uncertainty of the

average values, for which the individual values vary from 47 to 220, but

may be more reasonable for the uncertainty in a single value at one wavelength. The reported data provided essentially no information on which a valid evaluation of the true random error could be based, which

would involve multiple measurements at each wavelength with each ref lactometer

Within the limitations of the available data, the figures in Table

5 give an estimate of the state of the art in reflectance measurements

in the participating laboratories.

Some general conclusions can be drawn from the results of this

round-robin test. The bias in the reported values can be largely eliminated

by proper use of the reflectance standards recently made available by
-6-

the National Bureau of Standards as SRM's 2019, 2020, 2021, and 2022

under the sponsorship of SERI. The errors are due partly to the use of

incorrect reflectance values for the reference standards, and partly to

100% line and zero-line errors. The white standards can be used to

check the values assigned to the reference standards, and also to

evaluate the 100% errors. The black standards can be used to detect,

and to help correct the zero line errors. The errors in the values

reported by the participating laboratories are larger than were expected,

and especially the errors in the measurement of solar absorptance. Such

errors introduce rather' large errors into the computations of the thermal

efficiencies of solar collectors from the measured absorptance of the

absorber.
•0 7

Appendix I

1. Instructions for Round Robin Test

Preparation of Samples

The reflectance of the samples may be significantly affected by

dirt or surface films that are not easily seen. They should be cleaned

before measurement, using the following procedure.

The white samples are glazed ceramic tiles that have been cut to

size. The ceramic body is porous, and would absorb water if not sealed.

The back and edges have been sealed with an epoxy base masonry sealant.

If this seal is breached, the sample may absorb water, particularly if

immersed. Absorbed water will change the reflectance, orimarily in the

infrared. The samples should be handled gently to avoid chipping or a breach of the seal, and should never be immersed in water. Momentary

exposure to water as described in the cleaning procedure will not affect

them if the seal is not broken.

The cleaning procedure is as follows for both black and white

samples

1. Rinse with tepid tap water.

2. Wash with a dilute solution of a mild liquid soap, such as Ivory

Liquid,^ using gentle rubbing with a soft cloth or rubber sponge. Never

use on abrasive cleaner.

3. Rinse with tepid tap water, to remove soap. *

A. Rinse with distilled water.

5. Blot dry with a fr&sh facial tissue. Do not rub.

6. Allow to air dry for at least 30 minutes before measuring.

Any other noncorrosive liquid soap is also suitable for this use.
8

Measurement Procedure

The data desired are the spectral directional-hemispherical reflectance

for near-normal incidence, including the specular component. In addition,

if you have the facilities, also the spectral directional-hemishperical

reflectance for angles of incidence of 15, 30, 45 and 60 degrees from

normal, including the specular component.

1. Calibrate your ref lectometer , using your normal procedure.

2. Measure the samples, using your normal procedure, m.aking

corrections as required.

3. Report data at 10 nm intervals over as m.uch of the wavelength

range of 250 to 2500 nm as your ref lectometer can cover.

4. Compute solar reflectance of the white sample and solar

absorptance of the black sample, using your normal procedures,

and report the results.

5. Send the data to

J. C. Richmond

Room B126 Metrology

National Bureau of Standards

Washington, DC 20234

Include with the data a detailed description of all procedures

used, including the manufacturer and model number of all

instruments used, the method of reducing data, and the solar

spectral distribution and method of computation used for

computing solar properties.
X

run

300

310

320 330 340

350

360

370 380

390

400 410

420

430

440

450

460

470

480

490

500 510

520

530

540

550

560 570

580

590

600

610 620 630

640

650 660

670

680

690

700 700

710

720

730 740

750

7 50 760 770

780 790

800

800 810

820

830

340

850

860 870

880

890

TABLE 1 - RESULTS OF ROUND ROBIN TEST ON WHITE SAMPLES

Ub 1 Lab 2 Lab 3 Ub 4

0 Cal Dlff P Cal Dlff P Cal Dlff P Cal Dlff

.134 .147 -.013 .1470 .147 .0000 .2126 .140 .0726 .1446 .147 -.0024

.1940 .190 .0040 .2212 .190 .0312 .1829 .190 -.0071

.2025 .238 -.0355 .2630 .238 .0250 .2365 .238 -.0015

.3251 .303 -.0221 .3241 .303 .0211 .3063 .303 .0033 .3304 .377 -.0466 .3995 .377 .0225 .3082 .377 .0032

.437 .451 -.014 .4556 .460 -.0044 .4783 .460 .0183 .4620 .451 .0110

.5377 .541 -.0033 .5614 .541 .0204 .5438 .533 .0108

.6118 .608 .0038 .6266 .608 .0186 .6119 .601 .0109

.6616 .654 .0076 .6739 .654 .0199 .6593 .648 .0113

.7025 .690 .0125 .7096 .690 .0196 .6937 .684 .0097

.703 .714 -.011 . 734 r .720 .0147 .7382 .720 .0182 .7245 .714 .0105 .7536 .737 .0166 .7537 .737 .0167 .7427 .731 .0117 .7663 .749 .0173 .7743 .749 .0253 . 7520 .742 .0100

.7755 .757 .0185 .7736 .767 .0166 .7631 .751 .0121

.7807 .762 .0187 .7782 .762 .0162 .7665 .756 .0105

.755 .761 -.006 .7824 .767 .0154 .7815 .767 -.0145 .7716 .761 .0106 .7890 .772 .0170 .7858 .772 .0138 .7770 .765 .0120

.7934 .776 .0174 .7891 .776 .0131 .7819 .770 .0119

.7994 .780 .0194 .7938 .780 .0138 .7867 .774 .0127 .8046 .787 .0176 .8010 .787 .0140 .7930 .781 .0120

.783 .787 -.004 .8114 .793 .0184 .8074 .793 .0144 .7993 .787 .0123

.8177 .799 .0187 .8125 .799 .0135 .8056 .793 .0126

.8229 .805 .0179 .8163 .805 .0113 .3111 .799 .0121 .8288 .811 .0178 .8217 .811 .0107 .8166 .805 .0116

.8339 .816 .0179 .8271 .316 .0111 .8231 .811 .0121

.813 .815 -.002 .8379 .820 .0179 .8295 .820 .0095 .8279 .815 .0129

-.8416 .825 .0166 .8346 .825 .0096 .8322 .819 .0132

.8451 .829 .0161 .8383 .829 .0093 .8351 .324 .0111

.8464 .831 .0154 .8367 .331 .0057 .8359 .826 .0099

.8484 .834 .0144 .3427 .834 .0087 .3402 .829 .0112

.832 .833 -.001 .8546 .837 .0176 .8468 .837 .0098 .8451 .833 .0121

* .8568 .839 .0178 .8484 .839 .0094 .8478 .835 .0123

.8591 .842 .0171 .8523 .842 .0103 .8497 .836 .0137 .8610 .843 .0180 .3546 .843 .0116 .8303 .838 .0123

.8638 .846 .0178 ,.8561 .846 .0101 .3513 .840 .0113

. 84

.838 .003 .8629 .844 .0189 .8567 .344 .0127 .3519 .338 .0139

.8628 .848 .0143 .8614 .343 .0134 .8561 .842 .0141

.8698 .851 .0188 .3646 .351 .0136 .3589 .344 .0149

.8722 .851 .0212 .8662 .851 .0152 .8609 .345 .0159

.8724 .853 .0194 .8660 .353 .0130 .8618 .847 .0148

.853 .851 .002

.354 .851 .003 .8745 .857 .0175 .3717 .857 .0147 .8642 .351 .0132

.8768 .858 .0188 .3667 .853 .0137

.8801 .859 .0211 .8690 .354 .0150

.8842 .860 .0242 .8699 .854 .0159

.8718 .861 .0108 .8877 .861 .0267 .8686 .855 .0136

.357 .856 .001

.358 .356 .002 .8903 .862 .0283 .8652 .856 .0092 .8986 .862 .0366 .3648 .356 .0088

.9008 .863 .0378 .3642 .857 .0072

.8768 .863 .0138 .9051 .863 .0421 .8628 .356 .0068 .9100 .861 .0490 .3636 .355 .0086

.356 .854 .002 .858 .854 . 004 . .9129 .860 .0529 .3637 .854 .0097

.9128 .862 .0508 .3604 .356 .0044

.8718 .860 .0118 .9136 .860 .0536 .3610 .354 .0070

.9129 .859 .0539 .3606 .853 .0076 .9100 .857 .0530 .8591 .852 .0071

.351 .350 .001 .9043 .856 .0483 .3588 .850 .0088

.8640 .855 .0090 .8977 .855 .0427 .8597 .849 .0107

.8860 .853 .0330 .3581 .847 .0111

.8780 .852 .0260 .8567 .846 .0107

.8692 .852 .0172 .8549 .345 .0099
\

nm

900

910

920

930

9A 0

950

960

970 980

990

1000

1010

1020

1030 1040

1050

1060

1070

1080 1090

1100

1110

1120 1130

1140

1150

1160 U70 1180

1190

1200

1210

1220

1230 1240

1250

1260 1270

1280

1290

1300 1310 1320

1330

1340

1350

1360 1370

1380 1390

1400 1410

1420

1430

1440

1450 1460

1470

1480

1490

1500

1510 1520

1530 1540

TABLE 1 - continued Ub 1 Lab 2 Lab 3 Lab 4

p Cal Diff 0 Cal Dlff P Cal Dlff P Cal Dlff

847 .845 .002 .8576 .352 .0056 .8645 .852 .0125 .8560 .845 .0110 .8590 .853 .0060 .8566 .845 .0116 .8584 .853 .0054 .8575 .846 .0115 .8566 .853 .0036 .8574 .846 .0114 .8644 .853 .0114 .8564 .853 .0034 .3585 .846 .0125

849 .846 .003 .8551 5853 .0021 .8586 .846 .0126 .8576 .853 .0046 .3585 .846 .0125 .8578 .853 .0048 .8589 .847 .0119 .8685 .856 .0125 .8585 .856 .0025 .8595 .849 .0105 .8598 .856 .0038 .8624 .849 .0134

851 .851 .000 .8604 .858 .0024 .3631 .851 .0121 .8618 .859 .0028 .8630 .852 .0110

.8733 .860 .0133 .8652 .860 .0052 .8636 .853 .0106 .8661 .860 .0061 .8631 .854 .0091

.8692 .861 .0082 .8626 .855 .0076

.356 .856 .000 .8703 .861 .0093 .8625 .856 .0065 .3708 .861 .0098 .8692 .861 .0082 .8626 .857 .0056 .8709 .861 .0099 .8627 .857 .0057 .8708 .862 .0083 .3627 .857 .0057 .8698 .862 .0078 .8641 .857 .0071

,860 .857 .003 .8698 .861 .0088 .8686 .361 .0076 .8650 .857 .0080 .8670 .862 .0050 .8655 .857 .0085

.8707 .865 .0057 .8665 .860 .0065

.8742 .868 .0062 .8686 .862 .0066 .3778 .869 .0088 .8748 .869 .0058 .8696 .864 .0056

,867 .865 .002 .8783 .870 .0083 .3710 .865 .0060 .8777 .871 .0067 .8716 .867 .0046 .8795 .871 .0085 .8726 .367 .0056

.8798 .871 .0088 .8812 .871 .0102 .8730 .866 .0070 .8826 .371 .0116 .8740 .867 .0070

.870 .867 .003 .8833 .872 .0113 .8740 .867 .00 70 .8823 .872 .0103 .8732 .867 .0062

.’8809 .872 .0089 .8828 .872 .0108 . 8732 .867 .0062 .8818 .872 .0098 .8737 .867 .0067 .8827 .871 .0117 .8737 .867 .0067

.872 .868 .004 .8826 .872 .0106 .8741 .868 .0061 .8806 .873 .0076 .8852 .373 .0122 .8737 .368 .0057 .8834 .371 .0124 .8736 .867 . 0066

.8817 .871 .0107 .8723 .367 .0053 .8798 .871 .0088 .8722 .867 .0052

.870 .866 .004 .8791 .870 .0091 .8806 .870 .0106 .8732 .866 .0072 .8809 .870 .0109 .3726 .866 .0066

.8807 .870 .0107 .3731 .866 .0071 .8800 .870 .0100 .8726 .866 . 0066

.8838 .869 .0148 .8806 .869 .0116 .8726 .866 .0066

.870 .865 .005 .8837 .869 .0147 .8727 .365 .0077 .8875 .869 .0185 .8710 .865 .0060 .8916 .869 .0226 .3710 .865 .0060

.8831 .367 .0161 .9116 .367 .0446 .8699 .364 .0059 .9074 .866 .0414 .8711 .862 .0091

.866 .862 .004 .8939 .366 .0279 .8691 .362 .0071

.8859 .867 .0189 .3702 .863 .0072

.3832 .867 .0162 .3848 .867 .0178 .8697 .863 .0067 .8830 .868 .0150 .8707 .863 .0077 .8846 .867 .0176 .8712 .363 .0082

.869 .863 .006 .8836 .867 .0166 .8708 .363 .0078 .8833 .867 .0163 .8826 .867 .0156 .3707 .363 .0077 .8831 .866 .0171 .8707 .862 .0087 .8825 .865 .0175 .8702 .361 .0092 .8806 .863 .0176 .8701 .359 .0111

.864 .859 .005 .8741 .863 .0111 .8770 .863 .0140 .8700 .359 .0110

.8818 .867 .0148 .8722 .864 .0082

.8848 .869 .0158 .8747 .866 .0087 .8851 .871 .0141 .8747 .866 .0087 .8830 .871 .0120 .8858 .871 .0148 .3748 .866 .0088
TABLE 1 - continued

X Ub 1 na P Cal Dlff

1550 1560

1570

1580 1580

.874 .867 .007

1600 1610 1620

1630

1640

.873 .868 .005

1650

1660

1670 1680

1690

.873 .867 .006

1700 1710

1720 1730

1740

.872 .867 .005

1750

1760

1770

1780 1790

.871 .865 .006

1800

1810 1820

1830 1840

.870 .865 .005

1850

1860

1870

1880 1890

.869 .861 .008

1900

1910

1920

1930 1940

.857 .352 .005

1950

1960

1970 1980

1990

.865 .859 .006

2000

2010

2020 2030

2040

.866 .863 .003

2050 2060

2070 2080

2090

.870 .865 .005

2100 2110

2120

2130

2140

.874 .867 .007

2150

2160 2170

2180

2190

.874 .363 .011 P

.P.887

.8841

.8836

.8840

.8821

.8826

.8807

.8772

.8682

.8807

.8757

.8799

.8787

.8872

.8828

Ub 2 Cal

.872

.872

.872

.871

.870

.870

.868

.865

.854

.863

.867

.870

.869

.871

.869

Dlff

.0167

.0121

.0116

.0130

.0121

.0126

.0127

.0122

.0142

.0177

.0087

.0099

.0097

.0162

.0138

Lab 3 P Cal Dlff

.8876 .871 .0166

.8874 .871 .0164 .8873 .871 .0163

.8884 .872 .0164 .8876 '.872 .0156

.8877 .872 .0157

.8875 .872 .0155

.8877 .872 .0157 .8873 .871 .0163

.8884 .872 .0164

.8878 .872 .0158

.8883 .872 .0163

.8887 .872 .0167 .8899 .372 .0179 .8883 .871 .0173

.8900 .871 .0190

.8892 .871 .0182 .8894 .871 .0184 .8885 .870 .0185 .8871 .870 .0171

.8869 .870 .0169 .8856 .870 .0156

.8862 .870 .0162

.8866 .870 .0166

.8861 .870 .0161

.8871 .870 .0171

.8811 .869 .0121 .8868 .868 .0188

.8846 .868 .0166

.8858 .867 .0188

.8886 .866 .0226

.8857 .865 .0207

.8897 .865 .0247

.8844 .861 .0234

.8784 .856 .0224

.8778 .854 .0238

.8793 .856 .0233

.8830 .860 .0230

.8837 .862 .0217

.8843 .863 .0213

.8836 .863 .0206

.8862 .865 .0212

.8892 .867 .0222

.8903 .867 .0233

.8999 .868 .0319

.8921 .869 .0231

.8954 .869 .0264 .8980 .870 .0280

.9041 .870 .0341

.9038 .870 .0338

.9043 .870 .0343

.9049 .869 .0359

.9079 .870 .0379

.9131 .870 .0431

.9088 .871 .0378

.9148 .871 .0438

.9122 .873 .0392

.9156 .872 .0436

,9146 .870 .0446

,9145 .869 .0455

,9128 .867 .0458

Ub 4 P Cal Diff

.8748 .867 .0078

.8752 .867 .0082

.8752 .867 .0082

.8766 .867 .0096

.8761 .368 .0081

.8766 .868 .0086

.8766 .868 .0086

.8761 .868 .0081

.8753 .367 .0083

.8753 .867 .008 3

.8753 .867 .003 3 .8757 .367 .003 7 .8758 .367 .0088

.8757 .,367 .003 7 .8749 .867 .0079

.8753 .867 .008 3 .8749 .867 .0079 .3753 .366 .009 3 .8743 .866 .008 3 .8744 .365 .0094

.8733 .865 . 008 3 .8743 .365 .0091 .8742 .365 .004 3 .8738 .865 .00.3.4 .8738 .864 .0093

.8739 . 863 .0089 . 3738 .364 .009- .3738 .863 .0105

.8732 .863 .010:

.8724 .862 .0104

.3709 .361 .00P9

.8723 .861 .0113

.3672 . 56i .8671 .336 .01] 

.8659 . S 52 .01 30

.8606 .352 .8601 .35- .'''•4 1 .8631 .356 .0^171 .3650 . 5 53 .O^'O

.8686 .359 .0096

.8705 .350 .0115 .3701 .361 .0091 .3729 .362 .0119

.8733 .363 .0103

.3744 .36-. .0104

.8760 .863 .0130

.8776 .364 .0136

.3777 .365 .0127 .8784 .366 .0124 .3776 .366 .0116

.8791 .865 .0141 .3731 .365 .0131 .8792 .365 .0142 .8798 .366 .0138 .3808 .867 .0138

.3804 .867 .0134 .8811 .368 .0131 .3827 .868 .0147 .3798 .866 .0138 .8775 .864 .0135

.8754 .363 .0124 .3751 .861 .0141

.8714 .858 .0134 .8682 .355 .0132 .8641 .852 .0121

.8769 .860 .0169
TABLE 1 - continued

X Lab 1 Lab 2 Ub 3 Lab 4 na 0 Cal Dlff 8 Cal Dlff 0 Cal Dlff 8 Cal Dlff

2200 .860 .851 .009 .8650 .851 .0104 2210 ,8639 .851 .0129 2220 .3637 .858 .0057 .8610 .852 .0090

2230 .8671 .854 .0131 2240 .8649 .855 .0099

2250 .862 .856 .006 .8668 .856 .0108 2260 .8673 .859 .0083 .8653 .856 .0093 2270 .8665 .858 .0085 2280 ,8674 .858 .0094 2290 .8657 .859 .0067

2300 .867 .859 .008 J668 .360 .0068 .8678 .859 .0088 2310 .8744 .860 .0144

2320 .8732 .861 .0122 2330 .8723 .863 .0093 2340 .8804 .863 .0174 .8731 .863 .0101

2350 .869 .862 .007 .8721 .862 .0101

2360 .8715 .361 .0115 2370 .8702 .859 .0112 2380 .8775 .859 .0185 .8669 .859 .0079 2390 .8671 .858 .0091

2400 .866 .852 .014 .8656 .852 .0136

2410 .8623 .854 .0083 2420 .8642 .851 .0132 .8667 .851 .0157 2430 .8611 .848 .0131 2440 .8556 .346 .0096

24 50 .858 .843 .015 .8570 .843 .0140 2460 . .8521 .842 .0101 .8513 .842 .009 3 2470 .8496 .840 .0096

2430 .8518 .839 .0128 2490 .8478 .838 .0098

2500 .8534 .839 .0144

N 47 86 185 220

"X .146 .9995 3.5086 2 .1339

:x2 * .001936 2.074143 -.09202732 .022S4661

X .003106 .01162 .01895 .00970

a .005677 .01036 .01177 .00313
TABLE 2 - RESULTS OF ROUND ROBIN TF-ST ON BLACK SAMPLES

\ Ub 1 Lab 2 Ub 3 Ub 4

run P Cal Diff P Cal Dlff P Cal Dlff P Cal Diff

300 .049 .057 -.008 .0559 .057 -.0011 .0701 .057 .0131 .0534 .057 -.0036

310 .0567 .057 -.0003 .0670 .057 .0100 .0534 .057 -.0036

320 .0573 .059 -.0017 .0658 .059 .0068 .0544 .059 -.0046

330 .0568 .059 -.0022 .0660 .059 .0070 .0574 .059 -.0016

340 .0598 .060 -.0002 .0668 .060 .0068 .0573 .060 -.0027

350 .053 .060 -.007 .0596 .060 -.0004 .0681 .060 .0021 .0563 .060 -.0037

360 .0613 .062 -.0007 .0694 .062 .0074 .0575 .062 -.0045

370 .0632 .063 .0002 .0712 .063 .0082 .0605 .063 -.0025

380 .0653 .065 .0003 .0741 .065 .0091 .0634 .065 -.0016

390 .0686 - .068 .0006 .0769 .068 .0089 .0643 .068 -.0037

400 ,064 .070 -.006 .0706 .070 .0006 .0770 .070 .0070 .0643 .070 -.0057

410 .0709 .071 -.0001 .0767 .071 .0057 .0652 .071 -.0058

420 .0710 .070 .0010 .0759 .070 .0059 .0662 .070 -.0038

430 .0708 .070 .0008 .0754 .070 .0054 .0663 .070 -.0037

440 .0704 .069 .0014 .0749 .069 .0059 .0644 .069 -.0046

450 .063 .069 -.006 .0701 .069 .0011 .0745 .069 .0055 .064 5 .069 -.0045

460 .0702 .069 .0012 .0744 .069 .0054 .064 5 .069 -.0045

470 .0698 .069 .0008 .0742 .069 .0052 .0635 .069 -.0055

480 .0702 .069 .0012 .0736 .069 .0046 .0645 .069 -.0045

490 .0691 .068 .0011 .0733 .068 .0053 .0634 .068 -.0046

500 .062 .068 -.006 .0689 .068 .0009 .0727 .068 .0047 .0634 .068 -.0046

510 .0687 .068 .0007 .0721 .068 .0041 .0644 .068 -.0036

520 .0680 .067 .0010 .0718 .067 .0048 .0612 .067 -.0058

530 .0681 .067 .0011 .0714 .067 .0054 .0613 .067 -.0057

540 .0681 .066 .0021 .0711 .066 .0051 .0622 .066 -.0038

550 .059 .066 -.007 .0676 .066 .0016 .0708 .066 .0048 .0613 .066 -.0047

560 .0672 .066 .0012 .0704 .066 .0044 .0616 .066 -.0044

570 .0662 .065 .0012 .0692 .065 .0042 .0614 .065 -.0036

580 .0663 .065 .0013 .0685 .065 .0035 .0593 .065 -.0057

590 .0653 .064 .0013 .0683 .064 .004 3 .0603 .064 -.0037

600 .053 .064 -.006 .0650 .064 .0010 .0678 .064 .0038 .0614 .064 -.0026

610 .0650 .064 .0010 .0677 .064 .0037 .0625 .064 -.0015

620 .0647 .064 .0007 .0675 .064 .0035 .0615 .064 -.0025

630 .0640 .064 .0000 .0675 .064 .0035 .0605 .064 -.0035

640 .0645 .063 .0015 .0674 .063 .0044 .0605 .063 -.0025

650 .053 .063 -.005 .0642 .063 .0012 .0677 .063 .0047 .0624 .063 -.0006

660 .0644 .063 .0014 .0673 .063 .0048 .0614 .063 - .0016

670 .0651 .063 .0021 .0681 .063 .0051 .0624 .063 -.0006

680 .064 5 .064 .0005 .0685 .064 .004 5 .0633 .064 -.0007

690 .0655 .064 .0015 .0687 .064 .0047 .0634 .064 -.0006

700 .059 .065 -.006

700 .059 .065 -.006 .0653 .065 .0003 .0666 .065 .0016 .0614 .065 -.0036

710 .0683 .065 .0033 .0671 .065 .0021

720 .0673 .065 .0023 .0662 .065 .0012

730 .0677 .065 .0027 .0642 .065 -.0003

740 .0660 .065 .0010 .0673 .065 .0023 .0643 .065 -.0007

750 .059 .065 -.006

750 .059 .065 -.006 .0701 .065 .0051 .0623 .065 -.0027

760 .0652 .065 .0002 .0624 .065 -.0026

770 .0677 .065 .0027 .0624 .065 -.0026

780 .0574 .065 -.0076 .0722 .065 .0072 .0624 .065 -.0026

790 .0716 .065 .0066 .0624 .065 -.0026

800 .060 .065 -.005

800 .061 .065 -.004 .0740 .065 .0090 .0624 .065 -.0026

810 .0762 .065 .0112 .0622 .065 -.0028

820 .0698 .066 .0038 .0741 .066 .0081 .0643 .066 -.0017

830 .0763 .067 .0093 .0654 .067 -.0016

840 .0759 .067 .0089 .0665 .067 -.0005

850 .065 .068 -.003 .0756 .068 .0076 .0675 .068 -.0005

860 .0676 .069 -.0014 .0745 .069 .0055 .0694 .069 .0004 870 .0729 .070 .0029 .0714 .070 .0014

880 .0729 .072 .0009 .0733 .072 .0013 890 .0776 .073 .0046 .0753 .073 .0023
TABLE 2 - continued

X Lab 1 Lab 2 Ub 3 Ub 4

nm P Cal Dlff P Cal Dlff P Cal Dlff P Cal Diff

900 .071 .074 -.003 .0781 .074 .0041 .0781 .074 .0041 .0773 .074 .0033

910 .0811 .077 .0041 .0812 .077 .0042

920 .0805 .079 .0015 .0842 .079 .0052 930 .0873 .082 .0053 .0872 .082 .0052

940 .0934 .085 .0084 .0920 .085 .0070 .0902 .085 .0052

950 .086 .089 -.003 .0902 .089 .0012 .0922 .089 .0032 960 .0933 .092 .0013 .0931 .092 .0011

970 .0968 .095 .0013 .0941 .095 -.0009

980 .0966 .097 -.0010 .0968 .097 -.0002 .0923 .097 -.0047

990 .1001 .099 .0011 .0923 .099 -.0067

1000 .095 .100 -.005 - .0984 .100 -.0016 .0912 .100 -.0088

1010 .1010 .100 .0010 .0902 .100 -.0098

1020 .1000 .100 .0000 .1014 .100 .0014 .0892 .100 -.0108

1030 .0961 .099 -.0029 .0872 .099 -.0118

1040 .0943 .098 -.0039 .0852 .098 -.0128

1050 .091 .097 -.006 .0960 .097 -.0010 .0832 .097 -.0138

1060 .0969 .095 .0019 .0953 .095 .0003 .0822 .095 -.0128

1070 .0901 .092 -.0019 .0801 .092 -.0019

1080 .0904 .090 .0004 .0782 .090 -.0108

1090 .0903 .087 .0035 .0762 .087 -.0108

1100 .080 .085 -.005 .0855 .085 .0005 .0828 .085 -.0022 .0743 .085 -.0107

1110 .0838 .083 .0008 .0733 .083 -.0097

1120 .0829 .081 .0019 .0713 .081 -.0097

1130 .0809 .079 .0019 .0683 .079 -.0107

1140 .0771 .077 .0001 ,0807 .077 .0037 .0633 .077 -.0037

1150 .071 .076 -.005 .0732 .076 -.0023 .0674 .076 -. 00->6 1160 .0776 .075 .0026 .0673 .075 -.0077

1170 .0744 .074 .0004 .0674 .074 -.0066

1180 .0763 .073 .0033 .0733 .073 .0003 .0674 .073 -.0056

1190 .0727 .072 .0007 .0684 .072 -.0036

1200 .067 .072 -.005 .0736 .072 .0016 .0684 .072 -.0036

1210 .0720 .072 .0000 .0682 .072 -.0033

1220 .0777 .072 .0057 .0722 .072 .0002 .0682 .072 -.0033

1230 .0734 .072 .0014 .0682 .072 -. 003 '^ 1240 .0708 .072 -.0012 .0632 .072 -.0033

1250 .069 .072 -.003 .0762 .072 .0042 .0692 .072 -.0023

1260 .0738 .072 .0018 .0697 .072 -.0023 .0692 .072 -. 0 ^12 '-' 1270 .0719 .072 -.0001 .0701 .072 -.0019

1280 .0739 .073 .0009 .0711 .073 - . Ooi '^ 1290 .0733 .073 .0003 .0711 .073 -. 001 ?

1300 .069 .074 -.005 .0774 .071 .0034 .0764 .074 .0024 .0721 .074 -.0019

1310 .0727 .075 -.0023 .0723 .075 -.0027

1320 .0762 .075 .0012 .0733 .075 - . no 1

1330 .0749 .076 -.0011 .0742 .076 -. 001 ' 1340 .0832 .078 .0052 .0792 .078 .0012 .0762 .078 -.0015

1350 .075 .079 -.004 .0807 .079 .0017 .0771 .079 -.0019 1360 .0810 .080 .0010 .0790 .080 -.0010

1370 .0871 .081 .0061 .0800 .081 -.0010

1380 .0901 .083 .0071 .0899 .083 .0069 .0810 .083 -.0020

1390 .0916 .084 .0076 .0831 .084 -.0009

1400 .081 .086 -.005 .0939 .086 .0079 .0840 .086 - . 0020

1410 .0902 .087 .0032 .0861 .087 -.0009

1420 .0954 .089 .0064 .0929 .089 .0039 .0881 .089 -.0009

1430 .0967 .090 .0067 .0900 .090 .0000 1440 .0922 .092 .0002 .0910 .092 -.0010

1450 .089 .094 -.005 .1000 .094 .0060 .0919 .094 -.0021

1460 .1005 .095 .0055 .0975 .095 .0025 .0919 .095 -.0031

1470 .0997 .097 .0027 .0929 .097 -.0041

1480 .1020 .098 .0040 .0940 .098 -.0040

1490 .1024 .100 .0024 .0949 .100 -.0051

1500 .096 .101 -.005 .1042 .101 .0032 .1029 .101 .0019 .0969 .101 -.0041

1510 .1016 .102 -.0004 .0989 .102 -.0031

1520 .1065 .104 .0025 .0999 .104 -.0041

1530 .1080 .105 .0030 .1009 .105 -.0041

1540 .1075 .106 .0015 .1083 .106 .0023 .1029 .106 -.0031
TABLE 2 - continued

X Lab 1 Lab 2 Lab 3 Lab 4

nm P Cal Dlff P Cal Dlff P Cal Dlff P Cal Dlff

1550 .102 .107 -.005 .1071 .107 .0001 .1037 .107 -.0033

1560 .1077 .108 -.0003 .1057 .108 -.0023

1570 .1107 .108 .0027 .1057 .108 -.0023

1580 .1136 .109 .0046 .1152 .109 .0062 .1058 .109 -.0032

1590 .1103 .109 .0013 .1058 .109 -.0032

1600 .105 .110 -.005 .1124 aio .0024 .1058 .110 -.0042

1610 .1126 .110 .0026 .1059 .110 -.0041

1620 .1183 .110 .0083 .1144 .110 .0044 .1058 .110 -.0042

1630 .1158 .111 .0048 .1057 .111 -.0052

1640 .1149 .111 .0039 .1057 .111 -.0053

1650 .106 .111 -.005 - .1161 .111 .0051 .1057 .111 -.0053

1660 .1186 .111 .0076 .1188 .111 .0078 .1057 .111 -.0053

1670 .1194 .111 .0084 .1067 • 111 -.0043

1680 .1156 .111 .0046 .1067 .111 -.0043

1690 .1171 .111 .0061 .1066 .111 -.0044

1700 .107 .111 -.004 .1136 111 .0026 .1183 .111 .0073 .1056 .111 -.0054

1710 .1198 .111 .0088 .1056 .111 -.0054

1720 .1174 .111 .0064 .1057 .111 -.0053

1730 .1154 .111 .0044 .1046 .111 -.0064

1740 .1155 .111 .0045 .1132 .111 .0022 .1036 .111 -.0074

1750 .105 .110 -.005 .1143 .110 .0043 .1026 .110 -.0074

1760 .1133 .110 .0023 .1017 .110 -.0083

1770 .1118 .110 .0018 .1007 .110 -.0093

1780 .1124 .109 .0034 .1067 .109 -.0023 .1007 . 109 -.0083

1790 .1123 .109 .0033 . 0997 . 109 -.0093

1800 .104 .109 -.005 .1103 .109 .0013 .0996 .109 -.0094

1810

‘ .1093 . 108 .0013 .0987 . 103 -.0093

1820 .1083 .108 .0003 .1050 .108 -.0030 .0978 . 108 -.0092

1830 .1159 .107 .0089 .0978 . 107 -.0092

1840 .1113 .107 .004 3 .0978 . 107 -.0092

1850 .101 .106 -.005 .1052 .106 -. 0008- .0969 . 106 -.0091

1860 .1096 .106 .0036 .1083 .106 .0023 .0960 .106 -.0100

1870 .1032 .105 -.0018 .0956 . 105 -.0094

1880 .1074 .105 .0024 .0966 . 105 -. 00.34 1890 .1015 .104 -.0025 .0965 .104 -.0073

1900 .098 .104 -.006 .1065 .104 .0025 .1085 .104 .0045 .0963 . 104 -. 00 "

1910 .1083 .104 .0043 .0961 .104 -.0079

1920 .0984 .103 -.0046 .0953 .103 -.0077

1930 .1109 .103 .0079 .0943 .103 -.0037

1940 .1043 .102 .0023 .1085 .102 .006 5 .0933 .102 -. 008

'

1950 .095 .102 -.007 .1041 .102 .0021 .0943 .102 -. 007 * 1960 .1076 .102 .0056 .0943 .102 -.0077

1970 .1083 .102 .0063 .0952 .102 -. 006,3 1980 .1020 .101 .0010 .1077 .101 .0067 .0951 . 101 -.0059

1990 .1017 .101 .0007 .0951 . 101 -.0059

2000 .094 .101 - 007 .1045 .101 .0035 .0930 .101 -.0030

2010 .1032 .101 .0022 .0929 .101 -.0031

2020 .1045 .100 .0045 .1087 .100 .0087 .0913 .100 -.0082

2030 .1058 .100 .0058 .0926 .100 -.0074

2040 .0966 .099 -.0024 .0935 .099 -.0055

2050 .093 .099 -.006 .1112 .099 .0122 .0934 .099 -.0056

2060 .1060 .099 .0070 .0857 .099 -.0133 .0933 .099 -.0057

2070 .1024 .099 .0034 .0932 .099 -.0058

2080 .0977 .099 -.0013 .0932 .099 -.0058

2090 .1076 .098 .0096 .0932 .098 -.0043

2100 .092 .098 -.006 .1011 .098 .0031 .1012 .098 .0032 .0922 .098 -.0053

2110 .0960 .098 -.0020 .0920 .098 -.0060

2120 .0988 .098 .0008 .0920 .098 -.0060

2130 .1051 .097 .0081 .0908 .097 -.0062

2140 .0966 .097 -.0004 .1000 .097 .0030 .0907 .097 -.0063

2150 .091 .097 -.006 .1350 .097 .0380 .0890 .097 -.0080

2160 .0894 .096 -.0066

2170 .0895 .096 -.0065

2180 .0991 .095 .0041 .0897 .095 -.0053 2190 .0898 .095 -.0052
TABLE 2 - conclaued

X Ub 1 Lab 2 Lab 3 Lab 4

QD 0 Cal Dlff P Cal Dlff 0 Cal Dlff 0 Cal

2200 .090 .096 -.006 .0889 .096 2210 .0892 .096 2220 .0947 .096 -.0013 .0894 .096 2230 .0894 .096 2240 .0895 .096

2250 .089 .096 -.007 .0895 .096 2260 .0970 .096 .0010 .0895 .096 2270 .0904 .096 2280 .0901 .096 2290 - .0908 .096

2300 .089 .096 -.007 .1029 .096 .0069 .0908 .096 2310 .0908 .096 2320 .0889 .096 2330 .0888 .096 2340 .0902 .096 -.0040 .0885 .096

2350 .088 .096 -.008 .0892 .096 2360 .0902 .096 2370 .0910 .096 2380 .0961 .096 .0001 .0908 .096 2390 .0918 .096

2400 .088 .096 -.008 .0907 .096 2410 .0896 .096 2420 .1079 .096 .0119 .0881 .096 2430 .0880 .096 2440 .0879 .096

2450 .088 ..096 -.008 .0889 .096 2460 .0979 .095 .0029 .0887 .095 2470 .0888 .095 2480 .0878 .095 2490 .0898 .095 2500 .0923 .095 -.0027

-Y -.262 .1529 .6641

2X2 .001538 .0095455 .00583857

M 47 86 186 1 -.00557 .00178 .00357

a -.00130 .00283 .00433

Dlff

-.0071 -.0068 -.0066

-.0066

-.0065

-.0065

-.0065

-.0056

-.0059

-.0052

-.0052

-.0052 -.0071

-.0072

-.0075

-.0068

-.0058 -.0050

-.0052 -.0042

-.0053

-.0064 -.0079 -.0080

-.0081

-.0071 -.0063

-.0062

-.0072

-.0052

-1.04 58 .00744336

220-.00475

.00366
TABLE 3 - REPORTED VALUES FOR SOLAR PROPERTIES

Property Lab 1 Lab 2 Lab 3 Lab 4 NBS

Reflectance

of White Sample

%

82.5

%

87.1

%

84.3

%

81.06^

83.66^

83. 77^

80.40

81.94®

83.33

Absorptance

of Black Sample 93.1 92.9 92.5 93.04^

92.98^

92.07

92.44

1. Beckman 5270 Spectroref lectometer - Halon powder

2. Beckman 5270 double-beam grating-filter instrument with high intensity source

3. Varian Cary 17D integrating sphere ref lectometer

4. Perkin-Elmer 340 - Halon standards

5. Beckman 5420 - Halon standards

6. Beckman 5420 - BaSO, standard

4

7. Cary 17 - Halon standard

8. For Comparison to Laboratories 1 and 4

For Comparison to Laboratories 2 and 3
TABLE 4 - PROCEDURES USED FOR COMPUTING SOLAR PROPERTIES

Laboratory 1

Laboratory 2

Laboratory 3

Laboratory 4

NBS -

- 100 Selected Ordinate Method, based on Thekaekara AM 1.5

solar spectral irradiance.

- Weighted Ordinate Method, based on NASA AM 1.5 TDSSID.

- ASTM E-424, Method A, Weighted Ordinate Method based on Parry Moon data.

- Weighted Ordinate Method, based on proposed revision of

ASTM E-424.

100 Selected Ordinate Method, based on ASTM E-44 direct

solar irradiance.
I'Diff

0

I

Diff

TABLE 5 - DIFTEREMCES AS FRACTION OF REPORTED SOLAR VALUES

Lab 1

0.0038

0.0069

-0.0033

0.0060

Lab 2 bab J

WHITE SAMPLES - SOLAR REFLECTANCE

0.0133 0.0225

0.0119 0.0140

black samples - SOLAR ABSORPTANCE

0.0019 0.0039

0.0030

Lab 4

0.0118

0.0038

0.0057

a 0.0047 0.0039
07 T T

I L 500 1000 1500 2000 2500

- Difference between the data reported by Laboratory

1 and the calibration data for the white sample, plotted as a function of wavelength.

Figure 1
- Difference between data reported by Laboratory 2 and calibration

data for Che white sample, plotted as a function ot wavelength. Figure 2
500 1000 1500 2000 2500

Figure 3 - Difference betveen data reported by Laboratory 3 and calibration

data for the white sample, plotted as a function of wavelength.
ure 4 - Difference between data reported by Laboratory 4 and calibration

data for the black sample, plotted as a function of wavelength.
i

Figure . 5 - Difference between the data reported by Laboratory

1 and the calibration data for the black sample, plotted as a function of wavelength.
Figure 6 - Difference betveen the data reported by Laboratory 2 and

calibration data for the black sample, plotted as a function

of wavelength.
Figure 7 - Difference betveen the data reported by Laboratory 3 and the

calibration data for the black sample, plotted as a function

of wavelength.
.01

Figure 8 - Difference between data reported by Laboratory 4 and the

calibration data for the balck sample, plotted as a function

of wavelength.

NBS«n4A (REV. 2«8C) U.S., DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET (See instructions)

1. PUBLICATION OR

REPORT NO.

NBSIR 81-2311

2. Performing Organ. Report No.

4. TITLE AND SUBTITLE

Analysis of Results of Mini Round Robin Reflectance Test

3. Publication Date

July 1981

5. AUTHOR(S)

Joseph C. Richmond

6. PERFORMING ORGANIZATION (If joint or other than MBS, see instructions) 7. Contract/Grant No. national bureau of standards

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

8. Type of Report & Period Covered

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street. City. State, ZIP)

Solar Energy Research Institute, Golden, CO 80401

10.

SUPPLEMENTARY NOTES

i I Document describes a computer program; SF-185, FlPS Software Summary, is attached.

11.

ABSTRACT (A 200-word or less factual summary of most significant in formation. If document includes a significant

bibiiography or literature survey, mention it here)

A mini round robin test was conducted in which four national laboratories participated. The spectral directional-hemispherical reflectance for near-normal incidence

of two samples, one black and one white, was measured in the wavelength range of

250 to 2500 nm. The solar reflectance of the white sample and the solar absorptance

of the black sample was then computed. Each laboratory used a different procedure

for making the computations. The measured samples had previously been calibrated

in the Radiometric Physics Division of the National Bureau of Standards for

certification as reflectance standards. The average difference between the reported

values and the calibration values varied from +0.0116 +0.0634 to 0.0386 +0.0205 for

the white samples and from -0.00475 +0 to +0.00357 +0.00433 for the black

samples. The differences for the white samples were ascribed primarily" to errors

in the reflectance value assigned to the reference standard used in the measurements

The differences for the black samples were ascribed primarily to zero line errors.

12.

KEY WORDS (Six to twelve entries; alphabet! cal order; capitalize only proper names; and separate key words by semicolon s) diffuse reflectance; directional-hemispherical reflectance; integrating spheres;

laboratory intercomparisons; reflectance measurements; reflectance standards; solar

properties of materials; spectral reflectance measurements.

13.

AVAILABILITY

f^i Unl imi ted

I I For Official Distribution. Do Not Release to NTIS

i I Order From Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402.

I I Order From National Technical Information Service (NTIS), Springfield, VA, 22161

14. NO. OF

PRINTED PAGES

15. Price

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