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we wish to estimate the proportion of all college students who are working while going to school to within 4% at the 90% confidence level. we believe the true proportion is around 40%. how large a sample should we take to get the desired accuracy?

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To estimate the sample size required for estimating the proportion of college students who are working while going to school with a desired accuracy of 4% at a 90% confidence level, we can use the following formula:

n = (Z^2 * p * (1-p)) / (E^2)

where:

n is the sample size

Z is the Z-score corresponding to the desired confidence level (90% confidence level corresponds to a Z-score of 1.645)

p is the estimated proportion (or expected proportion) of the population

E is the desired margin of error

Given:

Desired accuracy (E): 4% or 0.04

Confidence level (Z-score): 1.645 (corresponding to 90% confidence level)

Estimated proportion (p): 0.40 (or 40%)

Plugging the values into the formula, we get:

n = (1.645^2 * 0.40 * (1-0.40)) / (0.04^2)

n = 0.1239 / 0.0016

n ≈ 77.4375

Rounding up to the nearest whole number, the estimated sample size required to achieve the desired accuracy is 78.

So, a sample size of at least 78 college students would be needed to estimate the proportion of college students who are working while going to school with a margin of error of 4% at a 90% confidence level, assuming an estimated proportion of 40%.

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