A swimming pool is open for 7 1/2 hours during a day. The pool keeps one lifeguard on duty at a time, and each lifeguard’s shift is 1 1/2 hours long. How many shifts are there per day?

Amayoral candidate would like to know her residents’ views on a public open space before the mayoral debates. she asks only the people in her office. her co-workers are an example of a census population convenience sample simple random sample