Rachel works in the school store at Miller Middle School. The store sells notebooks, pens, pencils and healthy snack bars. Rachel wanted to estimate the percentage of the students who bought the snack bars in the school store. There are 800 students in the school. She selected a random sample of 30 students who shopped at the school store during a two-month period. She determined that 15% of those students purchased a healthy snack bar. Which statement about Rachel’s sample is true?