Posted by **Josh** on Thursday, June 28, 2012 at 12:07am.

The diameter of small Nerf balls manufactured at a factory in China is expected to be approximately normally distributed with a mean of 5.2 inches and a standard deviation of .08 inch. Suppose a random sample of 20 balls is selected. Find the interval that contains 87% of the sample means.

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**PsyDAG**, Thursday, June 28, 2012 at 10:44am
87% = mean ± 1.51 SEm

SEm = SD/√n

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**Josh**, Thursday, June 28, 2012 at 5:48pm
What is square root n?

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**dave**, Sunday, July 1, 2012 at 8:55pm
The diameter of small Nerf balls manufactured at a factory in China is expected to be approximately normally distributed with a mean of 5.2 inches and a standard deviation of .08 inch. Suppose a random sample of 20 balls is selected. Find the interval that contains 87% of the sample means

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