Question

The proportion of students who own a cell phone on college campuses across the country has increased tremendously over the past few years. It is estimated that approximately 90% of students now own a cell phone and 10% do not own a cell phone. Fifteen students are to be selected at random from a large university. Assume that the proportion of students who own a cell phone or do not own a cell phone at this university is the same as nationwide. What is the probability that all students in a simple random sample of 15 students own a cell phone (hint: find the equivalent probability of the number of students that do not own a cell phone)?

Answer 1

I am not sure about that hint.

I think it is .9^15 = .206

Answer 2

a study states that for a particular area, the average income per family is $35,569 and the standard deviation is $8256. what percentage of families in that area earn below $ 25,000