Question: Pressing pills A drug manufacturer forms tablets by compressing a granular material that contains the active ingredient and various fillers. The hardness of a sample from each batch of tablets produced is measured to control the compression process. The target value for the hardness is m = 11.5. The hardness data for a random sample of 20 tablets are
Is there convincing evidence at the 5% level that the mean hardness of the tablets differs from the target value?