A medical study used 96 people aged 65 or older. Half received daily supplements of vitamins and minerals. The other half received placebos. The number of days of illness were recorded. Were there any differences at the .05 level of significance?

An automobile insurance company surveyed 100 male and 100 female drivers to determine how many miles each drove in the past year. The distances (in thousands) were recorded. Were there any differences at the .05 level of significance?

A manufacturer of automobile air conditioners is evaluating two suppliers of condensers. Thirty automobiles were equipped with each supplier's condensers – sixty automobiles in total. The number of miles driven before each condenser needed service was recorded (in thousands). Were there any differences at the .10 level of significance?

To test whether regular aerobic exercise can reduce high blood pressure as well as medication, fifty patients were selected and half exercised three times per week while the other half took the standard medication. The percentage reduction in blood pressure was recorded. Were there any differences at the .01 level of significance?