Posted by **sally** on Saturday, May 23, 2009 at 4:57pm.

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**, Saturday, May 23, 2009 at 5:00pm
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**, Sunday, May 24, 2009 at 12:28pm
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.

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