Can telling a joke affect whether or not a customer in a coffee bar leaves a tip for the waiter? A study investigated this question at a coffee bar in France. The waiter randomly assigned coffee-ordering customers into three groups: one received a card telling a joke with their bill, another group received a card containing an advertisement for a local restaurant, and the third received no card. The results are shown below. Tip Joke Card Ad Card No Card Total Left Tip 32 (0.40) 16 (0.20) 24 (0.30) 72 No Tip 48 64 56 168 Total 80 80 80 240 Are validity conditions met to conduct a chi-square test of association? Yes, since 240 is larger than 20. Yes, since each cell in the table has at least 10 observations. Yes, since 80 is larger than 20. No, the sample is not a random sample of customers