Question

Try to find out how much time children spend on watching TV. How large should your sample be to be 90% confident that the population mean is within 15 minutes of the sample mean? Assume population standard deviation is 57 minutes. Show all of your calculations.

Answer 1

Solution :

Given that,

Population standard deviation = = 57

Margin of error = E = 15

At 90% confidence level the z is,

= 1 - 90%

= 1 - 0.90 = 0.10

/2 = 0.05

Z_/2 = Z_0.05 = 1.645

sample size = n = [Z_/2* / E] ²

n = [ 1.645 * 57 / 15]²

n = 39.07

Sample size = n = 40