Homework Help: stats

Posted by Carlos on Tuesday, October 9, 2012 at 10:46am.

The life of tires manufactured by Omega Tires Inc is believed to be normally distributed with a mean of 110,000 km and a standard deviation of 5,000 km. A random sample
of 200 tires is tested . What is the problability of the mean life of this sample being between 109,000 and 111,000 km?

stats - PsyDAG, Tuesday, October 9, 2012 at 1:18pm
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 scores.

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