Question

Assume that a sample is used to estimate a population proportion p. Find the 90% confidence interval for a sample of size 395 with 267 successes. Enter your answer as an open-interval (i.e., parentheses) using decimals (not percents) accurate to three decimal places. C.I. =

Answer 1

We need to construct the 90% confidence interval for the population proportion. We have been provided with the following information about the number of favorable cases:

Favorable Cases X =	267
Sample Size N =	395

The sample proportion is computed as follows, based on the sample size N = 395 and the number of favorable cases X = 267

The critical value for α=0.1 is . The corresponding confidence interval is computed as shown below: