Question

A study of 50 white mice showed that their average weight was 4.2 ounces. The standard deviation of the population is 0.7 ounces. Which of the following is the 90% confidence interval for the mean weight per white mouse?

Answer 1

Solution :

Given that,

Point estimate = sample mean = = 4.2 ounces

Population standard deviation =    = 0.7 ouncws

Sample size = n = 50

At 90% confidence level

= 1 - 90%  

= 1 - 0.90 =0.10

/2 = 0.05

Z/2 = Z_{0.05 = 1.645}

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

= 1.645 * ( 0.7 /  50 )

= 0.16

At 90% confidence interval estimate of the population mean is,

  ± E

4.2 ± 0.16

( 4.04, 4.36 )