Homework Help: science

Posted by Joy on Sunday, January 22, 2012 at 5:38pm.

Shown below are the data giving the length of life of lights in an underground tunnel.

9.0 months 7.0 months
8.2 months 8.3 months
7.8 months 8.1 months
7.5 months 7.6 months
9.1 months 7.4 months

I calculated the standard deviation to be about 0.679.
Estimate the probability that a random chosen light will last as long as 7 months after installation. Assume the data to be described by a normal distribution.

Can anyone help me with the process I would use to calculate the answer? Thanks!

science - PsyDAG, Monday, January 23, 2012 at 11:39am
I assume that you have calculated the mean to find the SD.

Z = (score-mean)/SD

Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion related to the Z score.

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