Re: Questions regarding Multi -Lab MRL Calculations / Understanding

Technical Support Document

Brenda Parris to: Steve Via 05/02/2011 05:20 PM

Cc: "Jeff.Rosen@tetratech.com"

Hello Steve,

Our response to your questions are listed below. I am sorry that I was unable to schedule a meeting late

last week. Please let me know if you would still like to have a meeting this week or next to clarify MRL

procedures, nomenclature, etc.. If so, respond with a few days/times that you and Jeff are available, and I

will coordinate schedules on EPA's side.

1. Page 7 of 24 equation 2 which appears pretty straight forward but is not standard notation

and is not documented, what is Uj<k ? Is this a union?

Answer 1. U is the union of a distinct pair of means .

2. Page 11 of 24 equation 8 is subscripted with “v” that is not defined anywhere. Similarly,

at the next set of equations (with no equation number), the a, b and c are now subscripted with

an s with no explanation.

Answer 2. A subscript of "v" refers to variance.

3. Page 16

–similar to the issues listed above for page 11 of 24, equation set 12

–av , ae ,

bv , be , cv , ce - would all benefit from some explanation.

Answer 3. A subscript of "v" refers to variance and a subscript of "e" refers to conditional mean

square error.

4. Page A2

–the notation w*ij is not explained in the general notation or in the text.

Answer 4. W* refers to robust weight . W*

_ ij are not normalized to sum to 1. The w

_ ij are.

Have a nice day,

Brenda Parris

Steve Via 04/26/2011 04:45:36 PM Ms. Paris, My apologies for the delay in getting s...

From: Steve Via <SVia@awwa.org>

To: Brenda Parris/CI/USEPA/US@EPA

Cc: "Jeff.Rosen@tetratech.com" <Jeff.Rosen@tetratech.com>

Date: 04/26/2011 04:45 PM

Subject: Questions regarding Multi-Lab MRL Calculations / Understanding Technical Support Document

Ms. Paris,

My apologies for the delay in getting several example questions together. The following illustrate the kinds of

challenges we are experiencing with the nomenclature in the support document:

1. Page 7 of 24 equation 2 which appears pretty straight forward but is not standard

notation and is not documented, what is U

j <k ? Is this a union?

2. Page 11 of 24 equation 8 is subscripted with “v” that is not defined anywhere. Similarly,at the next set of equations (with no equation number), the a, b and c are now

subscripted with an s with no explanation.

3. Page 16

– similar to the issues listed above for page 11 of 24 equation set 12

– a

v , a

e , b

v ,

b

e , c

v , c

e ‐ would all benefit from some explanation.

4. Page A2

– the notation w *

ij is not explained in the general notation or in the text.

Thank you for your assistance helping us understand the technical support document. If you

can arrange a conference call this week it would be most helpful. If that is not possible, we

would still like to get together and talk through the support document with the correct folks so

that we adequately understand the document.

Best regards,

Steve

________________________________________________________________________ American Water Works Association

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