Geometric means shall be used when at least ten individual data points are available. A geometric mean shall be calculated using individual measurement values. Geometric means may not be calculated using DMR monthly averages, unless the DMR monthly average is the result of only two measurements. If fewer than ten data points are available, the arithmetic mean shall be used. Arithmetic and geometric means shall be calculated according to Equations I-1 and I-2 in Appendix I, respectively.
Okla. Admin. Code § 252:606-6-5