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!

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