Question

A manufacturer claims that the mean lifetime of its lithium batteries is less than 1200 hours. A homeowner randomly selects 35 of these batteries and finds the mean lifetime to be 1180 hours with a standard deviation of 80 hours. Test the manufacturers claim. Use α = 0.05.

Answer 1

solution

this is the left tailed test .  

The null and alternative hypothesis is ,

H0 :   = 1200

Ha : <1200

Test statistic = z

= ( - ) / / n

= (1180 - 1200) / 80 / 35

= -1.48

P(z < -1.48 ) = 0.0694

P-value = 0.0694

= 0.05  

P-value >

do not Reject the null hypothesis .

There is no sufficient evidence to suggest that