Section 410IAC32-1-85. "Weighted arithmetic mean" defined

   (a) "Weighted arithmetic mean" means the arithmetic mean of sample results weighted by the number of subsamples in each sample. Its purpose is to give influence to a sample relative to the surface area it represents. The types of samples include the following:

(1) A single surface sample is comprised of a single subsample.

(2) A composite sample may contain from two (2) to four (4) subsamples of the same area as each other and of each single surface sample in the composite.

  (b) The weighted arithmetic mean is obtained by summing, for all samples, the product of the sample's result multiplied by the number of subsamples in the sample and dividing the sum by the total number of subsamples contained in all samples:

(1) the weighted arithmetic mean of a single surface sample containing sixty (60) micrograms per square foot;

(2) a composite sample of three (3) subsamples containing one hundred (100) micrograms per square foot; and

(3) a composite sample of four (4) subsamples containing one hundred ten (110) micrograms per square foot.

The equation is (60 + (3*100) + (4*110))/(1 + 3 + 4) = 100 micrograms per square foot. (Indiana State Department of Health; 410 IAC 32-1-85; filed Sep 10, 2003, 4:24 p.m.: 27 IR 466; errata filed Jun 14, 2010, 10:11 a.m.: 20100630-IR-410100396ACA; readopted filed Jul 14, 2011, 11:42 a.m.: 20110810-IR-410110253RFA) NOTE: Transferred from the Air Pollution Control Board (326 IAC 23-1-69.5) to the Indiana State Department of Health (410 IAC 32-1-85) by P.L.57-2009, SECTION 17, effective July 1, 2009.