Question

A consumer magazine is testing the lives of two kinds of flashlight batteries. Britelite battery claims...

A consumer magazine is testing the lives of two kinds of flashlight batteries. Britelite battery claims to give more life in normal use but is more costly than ordinary batteries. The magazine randomly purchases 50 Britelite batteries and 50 ordinary batteries. The Britelite batteries are found to have a mean life of 17.5 months of normal use with a standard deviation of 1.1 months. The ordinary batteries have a mean life of 14.7 months of normal use with a standard deviation of 1.3 months. Find a 95% confidence interval for the time difference in the lives of the batteries.  

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