A random sample of 175 adults was given an IQ test. It was found that 85 of them scored higher than 100

Question

A random sample of 175

adults was given an IQ test. It was found that 85

of them scored higher than 100

. Based on this, compute a 95%

confidence interval for the proportion of all adults whose IQ score is greater than 100

. Then find the lower limit and upper limit of the 95%

confidence interval.

Carry your intermediate computations to at least three decimal places. Round your answers to two decimal places. (If necessary, consult a list of formulas.)

Lower limit:

Upper limit:

Answer 1

n = sample size = 175

phat = sample proportion = 85/175 = 0.486

z-critical for 95% CI is 1.96

CI = phat +/- z-critical * sqrt(phat*(1-phat)/n)