A quality control officer tests bottles of shampoo to see if

A quality control officer tests bottles of shampoo to see if the filling machines are putting the proper amount in each bottle. They do not want to shut down production unless there is strong evidence indicating that the machines are not functioning properly. After testing a sample of bottles, the quality control officer decides to leave the filling machines operating. Actually, however, the filling machines are not operating properly. This is an example of what type of error? Why?

Solution

This is type 2 error, when we fail to reject null hypothesis even when null is false. (null = machines operate propertly)