Question

You’re a human factors engineer studying the impact that helmets worn by operators on a factory floor might receive during a particular repair operation. A random sample of 50 helmets worn during the operation show that 18 had received damage of some sort.

a. Find a 95% confidence interval for the true proportion of helmets that receive damage during the repair operation. Note that this could serve as a proxy for describing how dangerous the current repair operation is.

b. Using the point estimate obtained by the preliminary sample of 50, how many helmets should be tested to be 95% confident that the error in estimating the true proportion is less than 0.02?

c. Repeat the approach in part b but without the preliminary point estimate to provide a more conservative sample size. Think about what value of ?̂ would do that.

Answer 1