Posted by **bob** on Wednesday, March 30, 2011 at 10:13pm.

A university dean wishes to estimate the average number of hours his part-time instructors teach per week. The standard deviation is 2.6 hours. How large a sample must be selected if he wants to be 95% confident of finding whether the true mean differs from the sample mean by 1 hour?

- statistics -
**MathGuru**, Thursday, March 31, 2011 at 11:25am
Formula:

n = [(z-value * sd)/E]^2

...where n = sample size, z-value will be 1.96 using a z-table to represent the 95% confidence interval, sd = 2.6, E = 1, ^2 means squared, and * means to multiply.

Plug the values into the formula and finish the calculation. Round your answer to the next highest whole number.

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