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: