Posted by **chalulu** on Sunday, March 13, 2011 at 5:30pm.

A researcher at a major hospital wishes to estimate the proportion of the adult population of the U.S. that has high blood pressure. How large a sample is needed in order to be 99% confident that the sample proportion will not differ from the tgrue proportion by more than 4%?

- statistics -
**MathGuru**, Wednesday, March 16, 2011 at 8:50pm
Formula:

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

...where n = sample size, z-value will be 2.58 using a z-table to represent the 99% confidence interval, p and q represent proportions, E = .04, ^2 means squared, and * means to multiply.

Note: p and q will both be .5 if no value is stated.

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

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