An experiment was done to see whether Vitamin C prevents colds. 100 people were randomly assigned to treatment (2,000 mg Vitamin C daily) and 100 to control (2,000 mg placebo daily) The treatment group averaged 2.3 colds in a year with an SD of 1.6 and the control group averaged 2.6 colds with an SD of 1.9. The question is: Is this a real difference or is that just due to chance