Need help statistic question

Question

The owner of a small deli is trying to decide whether to discontinue selling magazines. He suspects that only 11% of his customers buy a magazine and he thinks that he might be able to use the display space to sell something more profitable. Before making a final decision, he decides that for one day he will keep track of the number of customers that buy a magazine. (a) Explain why this is a binomial experiment. 

(b) Assuming his suspicion that 11% of his customers buy a magazine is correct, what is the probability that exactly 5 out of the first 13 customers buy a magazine? Give your answer as a decimal number rounded to two digits. 

(c) What is the expected number of customers from this sample that will buy a magazine? 

Answer 1

Rinzi

It's binomial because each customer has 2 choices - to buy or not to buy.

For b, P(n) = N c n pⁿ (1-p) ^N-n

^{N c n = N choose n = N ! / (n ! (N-n) !)}

^{P(n) = chance of exactly n successes in N trials, p = probability of success}

So for b, you need to find P(5). So n=5, N = 13, p = 0.11. you can calculate this.

For the last you need to find 0. P(0) + 1. P(1) + 2.P(2) + .... 13. P(13)

Mike