Hypothesis test for single mean
An injector molder produces plastic pens. The process is planned to produce pens with a mean weight equal to 0.250 ounce. To investigate whether the injection molded is operating satisfactorily, 40 pens were at random sampled with a mean of 0.2525 and a standard deviation of .0022. Test at 5% and 1% whether the molder is operating satisfactorily.