# Z test for population mean

1. A battery was designed to last an average of 30 hours in a radio. Complaints are pouring in that the batteries are junk and do not perform as expected. You test 24 batteries and find :

X = 29.3

S = 2.95

Normality assumed

Is there sufficient evidence to indicate premature battery failure at the  = .05 level?

https://brainmass.com/statistics/z-test/test-population-mean-247986

#### Solution Preview

Hypothesis Testing (Z- Testing)

1. A battery was designed to last an average of 30 hours in a radio. Complaints are pouring in that the batteries are junk and do not perform as expected. You test 24 batteries and find :

X = 29.3

S = 2.95

Normality assumed

= .05 ...

#### Solution Summary

The solution provides step by step method for the calculation of Z test statistic and P value . Formula for the calculation and Interpretations of the results are also included.