The owner of a popular coffee shop believes that customers who drink coffee are more likely to use their own cup than customers who drink espresso. Customers using their own cups get a 5% discount, which is displayed on the receipt. The owner randomly selects 50 receipts from all coffee purchases and 50 receipts from all espresso purchases. For coffee purchases, 24 receipts showed that the customer used their own cup. For espresso purchases, 18 receipts showed the customer used their own cup. Based on the 99% confidence interval, (–0.13, 0.37), is the coffee shop owner’s claim justified?

The owner’s claim is justified because there are positive values for the proportion of customers who use their own cups.

The owner’s claim is justified because the interval contains both positive and negative values for the difference in the proportions.

The owner’s claim is not justified because the interval contains nonpositive values. It is plausible that there is no difference, or that the proportion of espresso customers using their own cups is higher than the proportion of coffee customers using their own cups.