The picture below represents two lanes at the grocery store checkout, and the number of items in each cart.
So you're shopping, and in a hurry. You have ten items in your cart, so you can go into the 10-items-or-less express lane at the left. But there is one more thing you need/want. Do you put it in the cart, forcing you to the regular lane, or forget it and go into the left?
These are the questions we face when we go to the grocery store. How to get out as fast as we can. What matters more to you? The number of people in the line, or the number of items in the line?
An intrepid blogger did some regression analysis, and came up with some guidelines based on his findings. Here's one:
Check is slower than credit which is slower than cash. Students are sometimes surprised that cash is faster than credit. From my observations, the fastest cash transaction will outpace the fastest credit transaction by a wide margin but there is also huge variance in credit transactions. I mean, some people have absolutely no idea what they are doing with that thing. The same can't really be said of cash.
The express lane isn't faster. The manager backed me up on this one. You attract more people holding fewer total items, but… when you add one person to the line, you're adding 48 extra seconds to the line length (that's "tender time" added to "other time") without even considering the items in her cart. Meanwhile, an extra item only costs you an extra 2.8 seconds. Therefore, you'd rather add 17 more items to the line than one extra person!
I do profiling.
I look for the line with the fewest elderly. It's been my experience that either pay by check (takes forever) or, even worse, get out their mini-purses and pay by exact change down to the penny.
I also admit: I tend to avoid lines with dishevelled people (although, typically, I am often one). Food stamps and all that.
What about you?