Mary wants to know which type of book is most commonly checked out by visitors at the library. she surveys people in the children's room between 1pm and 2pm. which statements about Mary's survey are true?
a. Mary's sample is not representative because not all library visitors go to the children's reading room
b. Mary's sample is a representative of the population
c. mary will get a random sample by surveying as many people as possible in the children's reading room
d. the results of Mary's survey include a mode, but neither a mean nor a median