Posted by sally on .
The lifetimes of lightbulbs of a particular type are normally distributed with a mean of 290 hours
and a standard deviation of 6 hours. What percentage of the bulbs have lifetimes that lie within 1
standard deviation to either side of the mean?

Statistics 
Ms. Sue,
You're more likely to get help from an expert in this field if you use your School Subject in the above box.

Statistics 
PsyDAG,
Approximately 34% of scores lie between the mean and one standard deviation in any normal distribution. Therefore, μ ± 1 SD contains approximately 68% of the cases.
I hope this helps. Thanks for asking.