Question

Paul will select a random sample of students to create a 95 percent confidence interval to estimate the proportion of students at his college who have a tattoo. Of the following, which is the smallest sample size that will result in a margin of error of no more than 5 percentage points?

Answer 1

385

Explanation:

Given that:

Margin of Error (MOE) = 5% = 0.05

Zcritical, 95% = Z(1-α/2) = Z0.025 = 1.96

MOE = Zcritical * (√p(1-p))/n)

p is taken as 0.5 when not stated ;

5 = 1.96 * sqrt[(0.5 * 0.5) / n]

5 = 1.96 * sqrt(0.25/n)

Square both sides

(0.05/ 1.96)² = 0.25/n

0.0006507 = 0.25/n

0.0006507 * n = 0.25

n = 0.25 / 0.0006507

n = 384.20162

Sample size = 385