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Posted by on Monday, December 12, 2011 at 10:10pm.

The lifetime of a certain smart phone battery has an
unknown distribution with mean value of 8 hours and
standard deviation of 2 hours. What is the approximate
probability that the average battery lifetime of a sample
of 36 batteries will exceed 8.1 hours?

  • Statistics - , Wednesday, December 14, 2011 at 11:03am

    Assuming a normal distribution,

    Z = (score-mean)/SEm

    SEm = SD/√n

    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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