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A researcher wishes to be 95% confident that her estimate of the population proportion of individuals who travel overseas is within 4% of the true proportion. Find the sample size necessary. In a prior study, a sample of 200 people showed that 80 traveled overseas last year.

Formula to find sample size:

n = [(z-value)^2 * p * q]/E^2
... where n = sample size, z-value is found using a z-table for 95% confidence (which will be 1.96), p = 80/200, q = 1 - p, ^2 means squared, * means to multiply, and E = .04

Convert all fractions to decimals, then plug values into the formula and calculate n.

I hope this will help get you started.

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