There are

ways of pairing up any 2 members from the pool of
contestants. Note that

so that

Z score=(data value-mean)/standard deviation
z=(90-100)/15=-0.6666666667
However, the dosimeter is actually worn by the worker to determine the personal noise dose during the workshift or sampling period (Figure 21). Noise dosimetry is a form of personal sampling, averaging noise exposure over time and reporting results such as a TWA exposure or a percentage of the PEL.