A number of restaurants feature a device that allows credit card users to swipe their cards at the table. It allows the user to specify a percentage or a dollar amount to leave as a tip. In an experiment to see how it works, a random sample of credit card users was drawn. Some paid the usual way, and some used the new device. The percent left as a tip was recorded and listed below. Can we infer that users of the device leave larger tips?
Usual 10.3 15.2 13.0 9.9 12.1 13.4 12.2 14.9 13.2 12.0
Device 13.6 15.7 12.9 13.2 12.9 13.4 12.1 13.9 15.7 15.4 17.4