proportion of students who own a cell phone on college campuses across the count

Question

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 the number of phone. Fifteen students are to be selected at random from a large university. Assume that the proportion of students who own a cell phone at this university is the same as nationwide. Let X students in the sample of 1S who own a cell phone. What is the probability that all students in a simple random sample of 15 students own a cell phone? 0.1 0.9 O 0.206 In a certain game of chance, your chances of winning are 0.2. Assume outcomes are independent and that you will play the game five times. What is the probability that you win all five times? O 0.04 0.00032 0.3277 O 0.6723 A one-question survey is to be distributed to a random sample of 1500 adults in Ohio. The question asks if they support an increase in the state sales tax from 5% to 6%, with the additional revenue going to education. Let p denote the proportion of adults in the sample who say they support the increase. Suppose that 40% of all adults in Ohio support the increase. How large of a sample would be needed to guarantee that the standard deviation, , is no more than 0.01? 100 1500 1000 O2400 Let X be a random variable with a binomial distribution B(24, 0.4). Then the proportion has a mean and a standard deviation of, respectively 0.4 and 0.01 0.4 and 0.1 9.6 and 2.4 9.6 and 5.76 O0.4 and 2.4 0. Let X be a binomial random variable with p = 0.35, what size sample would be required to make the standard deviation of the proportion p=-equal to 0.047

Explanation / Answer

How large of a sample would be needed to guarantee that the standard deviation, , is no more than 0.01?

Ans:

p = 0.4

SD = sqrt[p * (1-p)/n] 0.01

sqrt(0.4 * 0.6/n) 0.01

0.24/ n 0.0001

n 2400

D option

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