# Sample size

A personality test has a subsection designed to assess the "honesty" of the test-taker. Suppose that you're interested in the mean score, mu, on this subsection among the general population. You decide that you'll use the mean of a random sample of scores on this subsection to estimate mu. What is the minimum sample size needed in order for you to be 99% confident that your estimate is within 3 of mu? Use the value 21 for the population standard deviation of scores on this subsection.

Carry your intermediate computations to at least three decimal places. Write your answer as a whole number (and make sure that it is the minimum whole number that satisfies the requirements).

Please see the attached file for full problem description.

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#### Solution Preview

Standard deviation =s= 21

(sample mean-M )= 3 (to ensure estimate is within 3 of M )

sx=standard error of mean=s/square root of n

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#### Solution Summary

The sample size has been calculated.