# Math ---HELP!!!!!

posted by angela

If light bulbs have lives that are normally distributed with a mean of
2500 hours and a standard deviation of 500 hours, what percentage of
light bulbs have a life less than 2500 hours?

1. PsyDAG

Z = (score-mean)/SD

Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion/probability for the Z score. Multiply by 100.

2. PsyDAG

Z = (score-mean)/SD

Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion/probability for the Z score. Multiply by 100.

However, if you realize that the mean and median are the same in a normal distribution, you won't need to go through all that work.

3. PsyDAG

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