A random sample of 400 electronic components manufactured by a certain process is
tested, and 30 are found to be defective.
a. Let p represent the proportion of components manufactured by this process that
are defective. Find a 95% confidence interval for p.
b. How many components must be sampled so that the 95% confidence interval will
specify the proportion defective to within ±0.02?
c. (Hard) The company ships the components in lots of 200. Lots containing more than
20 defective components may be returned. Find a 95% confidence interval for the
proportion of lots that will be returned.