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.
this is the left tailed test .
The null and alternative hypothesis is ,
H0 : = 1200
Ha : <1200
Test statistic = z
= ( - ) / / n
= (1180 - 1200) / 80 / 35
P(z < -1.48 ) = 0.0694
P-value = 0.0694
do not Reject the null hypothesis .
There is no sufficient evidence to suggest that
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