speed test
Similar to the speed test used to test your internet connection, but this speed test is used to determine which checkout line is moving faster. It involves a snap judgment as to (1) which checkout clerk looks the least likely to encounter a situation in which they have to call the manager, and (2) which customers are least likely to have some sort of problem at checkout.
I used the speed test at Costco and got burned when the line I changed into was actually slower than the line I moved out of.