We set a small greeter by the soup. The unit spoke in a calm, even voice. I timed every greeting with a kitchen clock.
After six minutes the shoppers matched the pitch. They stopped blinking. They turned in tight squares and waited for a prompt.
I used six people on that aisle and six with a cashier. The second set is the control group. That means they did not meet the machine.
The sample size was adequate. It was not. The chance this was luck is low. People call that a p-value.
