The life, in hours, of a randomly chosen light bulb produced by a manufacturer is normally distribut

Question

The life, in hours, of a randomly chosen light bulb produced by a manufacturer is normally distributed with mean $1100$ and standard deviation $70$. How large a sample is required such that the probability that the mean life in the sample shall exceed $1120$ is not more than $5\%$?

Do you need to use Central Limit Theorem in your working?

Accepted Answer

$n=34$. The Central Limit Theorem is not required because the population is normally distributed.

Continuous Random Variables - Normal Models for Sample Means and Averages

Continuous Random Variables - Normal Models for Sample Means and Averages

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