It started with a math problem.
Dan Meyer, a Santa Cruz, California high school geometry teacher posted the photo, below, in his blog.
NUMBERS REPRESENT ITEMS IN EACH GROCERY BASKET
He put out the call to all of his friends (an equally math-loving cohort, it would seem): which lane would you choose?
It prompted endless discussion of variables and constraints, scalable models and linear regression (omg— a non-zero y-intercept).
The short answer: skip the Express Lane. More individual customers is slower than more individual items.
The real answer is that some problems resist logical solutions. There is no “all other things being equal” when dealing with human behavior.
There are still plenty of mathematics involved. Each item in a customer’s basket adds an average of 2.8 seconds to the checkout time. But each customer adds about 48 seconds before accounting for scanning a single item (How are you today? Do you have your Club Card with you? Will you be needing help to your car?….). That adds up to an extra 17 items that can be rung up before you would choose the line with an extra person.
There are a few hard and fast rules to help speed you on your way.
- Check is slower than credit. Both are slower than cash. And look out for the lady with a fistful of coupons.
- Lucky 13– the lines are almost always shorter if there is a Lane 13. Lots of superstitious people out there.
- Watch the faffing, the waiting systems industry term to describe the stretch of time when the customer organizes their belongings after checkout has concluded. Faffing can drag on.
- Prepare to wait in Washington D.C. With an average waiting time of 8:23, the supermarket lines are the slowest in the nation. (see map below)
And the surest way to stay out of the slow line? Steer clear if you see me in the market. I have an uncanny knack for picking the slowest.