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.

3 answers

87% = mean ± 1.51 SEm

SEm = SD/√n
What is square root n?
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