The manager in our school cafeteria is concerned about students who ask for a water cup when placing an order but fill the cup with a soft drink from the beverage fountain instead of filling the
cup with water. The manager selected a random sample of 80 students who asked for a water cup
when placing an order and found that 23 of those customers filled the cup with a soft drink from
the beverage fountain
• (a) Construct and interpret a 95 percent confidence interval for the proportion of all
students who, having asked for a water cup when placing an order, will fill the cup with a
soft drink from the beverage fountain.
The manager estimates that each student who asks for a water cup but fills it with a soft drink
costs the school cafeteria $0.25. Suppose that in the month of January 500 students ask for a
water cup when placing an order.
• (b) Use the confidence interval constructed in part (a) to give an interval estimate for the
cost to the restaurant for the month of January from the customers who ask for a water
cup but fill the cup with a soft drink.