200 people took part in a study involving a new headache medicine. After one week, the subjects were asked if they had a headache in the past week. According to the data in the
two-way table, what fraction of the people who were given the placebo did not have a
headache?
Given
medicine
Given
placebo
20
Total
30
50
Headache
No headache
120
30
150
Total
150
50
200