Why are some people randomly tested more than once?

“Am I being singled out? I just did a random last month? Mike never gets tested. I don’t think this thing is random at all!”

Those are not uncommon concerns among some safety-sensitive employees, and many employers have been challenged in court to demonstrate that their programs are truly random. The reality is that in a truly random selection process, a high probability exists that some employees will be selected several times while others may never be selected.

Why? Because after each selection, the employee’s name is returned to the same pool, and he or she becomes just as likely as anyone else to be selected next time

Random selections are generated from an unbiased computerized selection program. As such, every employee in the testing pool has an equal chance of being selected during each selection period. Some employees are selected multiple times during the calendar year, while others may not be selected at all.

An employee can be randomly selected multiple times during a calendar year. Employees have an equal chance of being selected in each selection period, regardless of prior selections. See this post for details.