Question

In a study of the accuracy of fast food drive thru orders Burger King had 264 accurate orders and 54 that were not accurate. Construct a 99% confidence interval estimate of the percentage of orders that are not accurate. Please explain the process.

Answer 1

We have given,

In a study of the accuracy of fast food drive thru orders Burger King had 264 accurate orders and 54 that were not accurate.

Therefore, total = 264 + 54 = 318

We can use here confidence interval formula

Where, Z is 2.58 for 99% confidence interval.

NORMSINV(1-(0.01/2))................................Z critical value by using Excel command.

Therefore,

=>(0.1155, 0.2241)

Therefore, we are 99% confident that true proportion/percentage of orders that are not accurate is between 11.55% to 22.41%