Exercise 5-28: Got a Tip?
a. These are explanatory variables.
b. Record the percentage tip per check (rather than looking at how much the amounts vary across
the different sizes of bills).
c. Yes, she can conduct an experiment; she can randomly determine whether or not she introduces
herself by name (or stands throughout).
d. If she conducts this as an experiment she can control for confounding variables and draw causeand-effect conclusions.
e. On a customer-to-customer level, she could flip a coin to decide whether or not to introduce
herself by name or to decide whether or not she stands or squats at the table. She could also flip a
coin to decide whether or not she wears a flower in her hair, but she would probably want to do this
on a shift-by-shift basis.