Question

1. We take a sample of 500 movies from a certain studio to find the average run time. We know the population standard deviation of movie run times is 20 minutes. What is the margin of error at 99% confidence?

Group of answer choices

.89

1.63

2.31

.10

Answer 1

Solution :

At 99% confidence level the z is ,

  = 1 - 99% = 1 - 0.99 = 0.01

/ 2 = 0.01 / 2 = 0.005

Z/2 = Z0.005 = 2.576   ( Using z table )

Margin of error = E = Z/2* ( /n)

=2.576* ( 20/ 500)

=2.31