Posted by **PK** on Tuesday, February 21, 2012 at 4:28pm.

The population standard deviation (σ) for a standardized achievement test that is normally distributed is 8.

a.) Calculate the standard error of the mean if you draw a random sample of 50 test scores. Show your work for full credit . . .

b.) Your sample mean is calculated to be 77. Compute the 95% confidence interval for the mean. Show your work!

c.) Interpret the meaning of the 95% confidence interval in one sentence.

- statistics -
**MathGuru**, Tuesday, February 21, 2012 at 4:49pm
Here are a few hints to get you started:

a). Standard error of the mean = standard deviation divided by the square root of the sample size

b). CI95 = mean ± 1.96(sd/√n)

...where ± 1.96 represents the 95% interval using a z-table, sd = standard deviation, and n = sample size

c). You are 95% confident that the population mean is within the interval.

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