The lifetime of a particular type of battery is normally distributed with a mean of 1100 days

Question

and a standard deviation of 80 days. The manufacturer randomly selects 400 batteries of this
type and ships them to a departmental store.

(a) What is the mean and standard deviation of the sampling distribution of X ?

(b) What is the probability that the average lifetime of these 400 batteries is between 1097
and 1104 days ?

Answer 1

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