Question

Apply the​ 68-95-99.7 rule to answer the question. The lifetimes of light bulbs of a particular type are normally distributed with a mean of 370 hours and a standard deviation of 7 hours. What percentage of the bulbs have lifetimes that lie within 2 standard deviations to either side of the​ mean?

Answer 1

95%.

Explanation:

We have been given that the lifetimes of light bulbs of a particular type are normally distributed with a mean of 370 hours and a standard deviation of 7 hours.

We are asked to find the percentage of the bulbs whose lifetimes lie within 2 standard deviations to either side of the​ mean using empirical rule.

The empirical rule (68-95-99.7) states that approximately 68% of data points lie within 1 standard deviation of mean and 95% of data points lie within two standard deviation of mean. 99.7% of data points lie within three standard deviation of mean.

Therefore, approximately 95% of data points lie within two standard deviation of mean.