Toyota provides an option of a sunroof and side air bag package for its Corolla model. This package costs $1400 ($1159 invoice price). Assume that prior to offering this option package, Toyota wants to determine the percentage of Corolla buyers who would pay $1400 extra for the sunroof and side air bags. How many Corolla buys must be surveyed if we want to be 95% confident that the sample percentage is within four percentage points of the true percentage for all Corolla buyers?
This solution finds the sample size necessary to estimate a population proportion.