Vitamin C and colds

One group of 139 skiers was given 1 gram ascorbic acid (vitamin C) per day and another group of 140 was given a placebo. Which skiers got colds?

     Cold      No cold  
Ascorbic acid 17 122
Placebo 31 109

Explain that contingency tables can arise from:

Vitamin C and colds
To test whether vitamin C reduces the risk of catching a cold, a 1961 French study involved 279 skiers over two periods of 5-7 days. Skiers in one group of 139 were given 1 gram ascorbic acid (vitamin C) per day whereas those in the other group were given a tablet that looked similar but had no active ingredient (called a placebo). None of the skiers knew which of the treatments they had received.
Drug screening of job applicants
The contingency tables show results from urine drug screening for 2537 applicants for career craft positions in the US Postal Service's Boston Management Sectional Center. Several other variables were recorded from each applicant.