Question

The lifetimes of light bulbs of a particular type are normally distributed with a mean of 270 hours and a standard deviation of 11 hours. What percentage of the bulbs has lifetimes that lie within 2 standard deviations of the mean on either side?

Apply the 68-95-99.7 rule to this questions.

Answer 1

I believe the "68-95-99.7 rule" means the percentage of observations within 1-2-3 standard deviations from the mean.

Try to apply the rule to answer the given question.

Answer 2

95%