We have 66 total employees: 42 in office A, 16 in office B, 6 in office C, and 2 in office D. We are discussing implementing monthly or quartery random drug tests and want to know the probability that an employee would be chosen from a particular office. We may have thought about this so much that we have confused ourselves, but basically we want to know that if we choose one employee out of the total of 66, what would be the chance the employee would come from office A, B, C, or D. We would then like to know how it would change if we pick two employees each month. Thanks for your help.

For two employees, I think the attached works it out for you.

HTH,

Alan.

Random-Drug-Tests---Version-001.xls