SCHEDULE 3STANDARDS
Methodology2
1
In this Schedule, “percentile value” is based on a percentile evaluation of the log10 normal probability density function of microbiological data used for the assessment under regulation 9.
2
SEPA must derive a percentile value as follows–
a
take the log10 value of all bacterial concentrations in the data sequence to be evaluated or, if a zero value is obtained, take the log10 value of the minimum detection limit of the analytical method used;
b
calculate the arithmetic mean (“μ”) of the log10 values taken under paragraph (a);
c
calculate the standard deviation (“σ”) of the log10 values taken under paragraph (a);
d
derive the upper 90-percentile point of the data probability density function from the following equation: upper 90-percentile = antilog (μ + 1.282 σ); and
e
derive the upper 95-percentile point of the data probability density function from the following equation: upper 95-percentile = antilog (μ + 1.645 σ).