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.
-Are validity conditions met to conduct a chi-square test of association?
A) Yes, since 80 is larger than 20.
B) Yes, since 240 is larger than 20.
C) Yes, since each cell in the table has at least 10 observations.
D) No, we did not collect a random sample of customers.

Question

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. 
-Are validity conditions met to conduct a chi-square test of association?
A) Yes, since 80 is larger than 20. 
B) Yes, since 240 is larger than 20. 
C) Yes, since each cell in the table has at least 10 observations. 
D) No, we did not collect a random sample of customers.

Quizplus · Accepted Answer

For a chi-square test of association, each cell in the contingency table should have at least 5 observations, and having at least 10 observations per cell is a stronger condition that ensures validity.

Can Telling a Joke Affect Whether or Not a Customer