In a survey of 100 people 40 were casual drinkers and 60 did

In a survey of 100 people, 40 were casual drinkers, and 60 did not drink. Of the ones who drank, 6 had minor headaches. Of the non-drinkers, 9 had minor headaches. Are the events \"drinkers\" and \"had headaches\" independent?

Solution

Yes, the events \"drinkers\" and \"had headaches\" are independent.