Question

In a certain year, 23% of all teenagers in the United States had checking accounts. Your bank, TeenChex Inc., is interested in targeting teenagers who do not already have a checking account. (a) If TeenChex selects a random sample of 1,000 teenagers, what number of teenagers without checking accounts can it expect to find? teenagers What is the standard deviation σ of this number? (Round the standard deviation to one decimal place.)

Answer 1

1. 770

2. 13.31

Explanation:

n = 1000

P (probability of those with account) = 23% = 0.23

q(probability of those without account) = 1-p = 0.77

a. We are expected to find the expected number of those without checking account

= n * q

= 1000 * 0.77

= 770

b. Standard deviation

= √n*p*t

= √1000x0.77x0.23

= √177.1

= 13.31