Posted by **John Davis** on Saturday, December 11, 2010 at 9:58pm.

Computer Services wants to estimate the mean number of hours college students use on campus computers each day. They want to be within .1 hour of the true value with 99% confidence. From a previous study, the standard deviation is assumed to be .6 hour. What size sample is needed? Show any work necessary to support your answer

- statistics -
**MathGuru**, Saturday, December 11, 2010 at 11:22pm
Formula:

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

...where n = sample size, z-value will be 2.575 using a z-table to represent 99% confidence, sd = .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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