Question

You measure 34 textbooks' weights, and find they have a mean weight of 35 ounces. Assume the population standard deviation is 8.9 ounces. Based on this, construct a 95% confidence interval for the true population mean textbook weight . Give your answers as decimals, to two places. ____ < μ < ____

Answer 1

Solution :

Given that,

Point estimate = sample mean =     = 35

Population standard deviation =    =8.9

Sample size n =34

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 * ( 8.9/ 34)

= 2.99
At 95% confidence interval estimate of the population mean
is,

- E < < + E

35 - 2.99 <   < 35 + 2.99

32.01 <   < 37.99