Psychologists were interested in whether there is a “denomination effect”—are people more or less likely to spend money if that money is in large bills or in lots of small bills? Such research may help give advice to people with problems controlling their spending, for example. The researchers stopped 50 people at a U.S. convenience store and asked them three simple questions; as a reward, they gave each person $5, either as a $5 bill or as five $1 bills. Of the 25 people who were given the larger bill, 4 spent some money in the convenience store. Of the 25 people who were given five $1 bills, 6 spent some money.

a. Is there a significant difference in the probability of spending money depending on the denomination of the bills received?

b. What is the relative risk of spending money for small bills compared to large bills?