A band director is trying to decide what music to play for the halftime show. To get a sample, the director divides the band into groups based on their grade (freshmen, sophomores, juniors, and seniors). Then she randomly chooses a group and surveys every member of the chosen group. Which sampling method was used? cluster sampling
simple random sampling
stratified random sampling
systematic random sampling

Quick! a survey of 57 customers was taken at a bookstore regarding the types of books purchased. the survey found that 33 customers purchased mysteries, 25 purchased science fiction, 18 purchased romance novels, 12 purchased mysteries and science fiction, 9 purchased mysteries and romance novels, 6 purchased science fiction and romance novels, and 2 purchased all three types of books. a) how many of the customers surveyed purchased only mysteries? b) how many purchased mysteries and science fiction, but not romance novels? c) how many purchased mysteries or science fiction? d) how many purchased mysteries or science fiction, but not romance novels? e) how many purchased exactly two types of books?

Me find the value of x each figure.

Erin bought christmas cards for $2 each to send to her family and friends. which variable is the dependent variable?