# Confidence interval for a population proportion

A researcher wishes to estimate the proportion of X-ray machines that malfunction. A random sample of 275 machines is taken, and 82 of the machines in the sample malfunction. Based upon this, compute a 90% confidence interval for the proportion of all X-ray machines that malfunction. Then complete the table below.

Carry your intermediate computations to at least three decimal places. Round your answers to two decimal places.

1. What is the lower limit of the 90% confidence interval? ____

2. What is the upper limit of the 90% confidence interval? ___

https://brainmass.com/statistics/confidence-interval/confidence-interval-population-proportion-15361

#### Solution Preview

A 90% confidence interval for a binomial proportion. Please see the attached Word document for details.

A researcher wishes to estimate the proportion of X-ray machines that malfunction. A random sample of machines is taken, and of the machines in the sample ...

#### Solution Summary

This solution shows how to calculate the upper and lower limits of a confidence interval for a population proportion.