Posted by **Blegh** on Saturday, November 3, 2012 at 2:29pm.

We guess, based on historical data, that 30% of graduating high-school seniors in a large city will have completed a first-year calculus course. What's the minimum sample size needed to construct a 95% confidence interval for a proportion with a margin of error of 2.5%?

1537

1291

1286

1533

1223

- AP Statistics -
**MathGuru**, Saturday, November 3, 2012 at 6:16pm
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 = .30, q = 1 - p, ^2 means squared, * means to multiply, and E = .025 (2.5%)

Convert all fractions to decimals, then plug values into the formula and calculate n. Round your answer to the next highest whole number.

- AP Statistics -
**Jessica**, Monday, April 8, 2013 at 8:08pm
1533

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