Question

You measure 29 textbooks' weights, and find they have a mean weight of 78 ounces. Assume the population standard deviation is 13.2 ounces. Based on this, construct a 95% confidence interval for the true population mean textbook weight. Round answers to at least 4 decimal places.

Answer 1

= Solution :

Given that,

Point estimate = sample mean = = 78

Population standard deviation =    = 13.2

Sample size n =29

At 95% confidence level the z is ,

= 1 - 95% = 1 - 0.95 = 0.05

/ 2 = 0.05 / 2 = 0.025

Z/2 = Z0.025 = 1.96   ( Using z table )

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

=1.96 * ( 13.2/   29)

= 4.8043
At 95% confidence interval estimate of the population mean
is,

-+ E

78+-4.8043

(73.1957 ,82.8043)