# Presentation: 215662

## Statistical Evaluation of Power

- Sielken  &  Associates Consulting Inc.
- 3833 Texas Avenue, Suite 230, Bryan, TX 77802
- Tel: 979-846-5175; Fax: 979-846-2671;
- Email: SielkenAssoc@aol.com

**Statistical Evaluation of Power**
**in**
**Human Sensory Irritation Testing **
**for Chloropicrin**

- Human Studies Review Board
- June 28, 2006

- Speaking on Behalf of the Chloropicrin Manufacturers Task Force

## As part of the experimental design 

- and prior to any human exposures,
- a statistical analysis of the
- proposed human sample sizes
- was done to ensure that the study had
- sufficient POWER
- to meet scientific standards
- and provide potential public health benefits.

## Determine the sample size such that

- Solution:
- With a random sample of size 60,
- the probability is > 0.87
- that between 85% and 95% of the sample
- will be able to detect a chloropicrin concentration
- that 90% of the population can detect.

- Problem:
- Determine the sample size such that
- the sample proportion detecting a chloropicrin concentration
- is sufficiently close to the true population proportion
- that would detect that chloropicrin concentration.

## The Phase 3 study has 80% power 

- The Phase 3 study has 80% power
- of observing at least one respiratory irritation
- in at least one of the 32 individuals
- (15 males and 17 females)
- if each individual's probability of a respiratory irritation
- following an exposure session at 0.10 ppm chloropicrin vapor
- is at least 0.005
- and the individual’s probability of a respiratory irritation
- following an exposure session at 0.15 ppm
- is 1.5 times that at 0.10 ppm.

## then an 80% upper confidence limit on 

- If there were no respiratory irritations observed
- at 0.10 ppm and 0.15 ppm,
- then an 80% upper confidence limit on
- the probability (p) of a respiratory irritation
- is 0.005
- Similarly, a 95% upper confidence limit on
- the probability (p) of a respiratory irritation
- is 0.009

- Phase 3 Chloropicrin Study: Statistical Power

## Statistical Power in the Phase 3 Chloropicrin Study:

- Experimental Design:

- Person:

| Fri | Sat | Sun | Mon | Tues | Wed | Thurs | Fri |
| --- | --- | --- | --- | --- | --- | --- | --- |
| Pre-
Test |  |  | Expos | Expos | Expos | Expos | Post-
Test |

| Fri | Sat | Sun | Mon | Tues | Wed | Thurs | Fri |
| --- | --- | --- | --- | --- | --- | --- | --- |
| Pre-
Test |  |  | Expos | Expos | Expos | Expos | Post-
Test |

| Fri | Sat | Sun | Mon | Tues | Wed | Thurs | Fri |
| --- | --- | --- | --- | --- | --- | --- | --- |
| Pre-
Test |  |  | Expos | Expos | Expos | Expos | Post-
Test |

- 0 ppm

- 0.10 ppm

- 0.15 ppm

- 0, 0.10, and 0.15 ppm in Random Order
- and  Weeks  apart

## Experimental Design:

- Person:

| Fri | Sat | Sun | Mon | Tues | Wed | Thurs | Fri |
| --- | --- | --- | --- | --- | --- | --- | --- |
| Pre-
Test |  |  | Expos
Day | Expos
Day | Expos
Day | Expos
Day | Post-
Test |

| Fri | Sat | Sun | Mon | Tues | Wed | Thurs | Fri |
| --- | --- | --- | --- | --- | --- | --- | --- |
| Pre-
Test |  |  | Expos
Day | Expos
Day | Expos
Day | Expos
Day | Post-
Test |

| Fri | Sat | Sun | Mon | Tues | Wed | Thurs | Fri |
| --- | --- | --- | --- | --- | --- | --- | --- |
| Pre-
Test |  |  | Expos
Day | Expos
Day | Expos
Day | Expos
Day | Post-
Test |

- 0 ppm

- 0.10 ppm

- 0.15 ppm

**Calculate Power**
**Accounting for **
**Possible Dependence**
**on 4 Exposure Days**

- 0, 0.10, and 0.15 ppm in Random Order
- and  Weeks  apart

## The Phase 3 study has 80% power 

- The Phase 3 study has 80% power
- of observing at least one respiratory irritation
- in at least one of the 32 individuals
- (15 males and 17 females)
- if each individual's probability of a respiratory irritation
- following an exposure session at 0.10 ppm chloropicrin vapor
- is at least 0.008    (vs 0.005 if 0% Correlation)
- and the individual’s probability of a respiratory irritation
- following an exposure session at 0.15 ppm
- is 1.5 times that at 0.10 ppm.

- Assuming 50% Correlation Between First Exposure Day
- and Each Subsequent Exposure Day

## Thank You