Question

You take a random sample of 500 apples from a shipment and construct a 95% confidence interval to estimate the proportion that has any residue of pesticides that have been banned by the FDA. You get a margin of error that is five times larger than you would like. What sample size should you use to obtain the desired margin of error?

You should use sample size of ___ apples.

Answer 1

Margin of error = Z*

If current margin of error is 5 times the desired margin of error,

Z* = 5 x Z* , where n₂ is the required sample size

=

= 5

n₂ = 25 x n

= 25 x 500

= 12,500

You should use sample size of 12,500 apples