a. What is the mean number of sales? b. What is the standard deviation of number of sales? c. Complete the table below.

Question

1.      The probability that a person buys a car from a particular dealership after a test-drive is 25%. From a sample of 100 people that took a test-drive,

a.      What is the mean number of sales?

b.     What is the standard deviation of number of sales?

c.      Complete the table below.

Number of sales	Probability of this number of success
21 to 29 sales
17 to 33 sales
At least 30 sales
At most 20 sales

Answer 1

I assume that a 'success' is selling a car. Then the probability of success is 0.25 (given in the problem). You also know that n=100. Such problems (only two possible outcomes) typically follow a binomial distribution.

The expected value, or mean, of a binomial distribution, is calculated by multiplying the number of trials (n) by the probability of successes (p), or n x p. For example, the expected value of the number of heads in 100 trials of head and tales is 50, or (100 * 0.5). Looks like you need to do these calculations for each row in the table( for part C), as well as in general( to answer parts a & b).

That should give you a good start on solving this problem.