Posted by **DezShonna K** on Friday, June 11, 2010 at 9:03pm.

The average age of statistics students nationwide is 22. The standard deviation is 2.5 years. Assume the age is a normally distributed variable.

Find the probability that one student selected at random is older than 23.

Find the probability that the mean age of a group of 16 students selected at random is bigger than 23

- statistics -
**PsyDAG**, Saturday, June 12, 2010 at 10:29am
Z = (score - mean)/SD

Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion above that Z score.

Z = (mean1 - mean2)/standard error (SE) of difference between means

SEdiff = √(SEmean1^2 + SEmean2^2)

SEm = SD/√(n-1)

Since only one SD is provided, you can use just that to determine SEdiff.

Use same table.

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