Grocery store checkouts

[mofoburrell]

For the past year or so, I’ve been tim­ing how long it takes for me to go through the check­outs at our gro­cery store to see which is faster.

The meth­od­o­logy is quite simple. Once I’ve got all my gro­cer­ies, I go to the same spot near the check­outs. To avoid bias­ing myself, I check my cell phone to determ­ine whether to go through the self check­outs or the nor­mal check­outs. Because my cell phone lacks a ran­dom num­ber gen­er­ator, I check the last digit of the time: an even digit means I go through the nor­mal check­out and an odd digit means I go through self check­out. I then start the stop­watch and time how long it takes for me to go through the check­out and leave the store.

I’ve got 31 data points and have finally decided that if one type of check­out is faster than the other, the dif­fer­ence is small enough to not really mat­ter. Here’s the scat­ter­plot:


A sample size of 31 is unim­press­ive, to be sure, but it’s large enough that I can finally rest easy know­ing it would be a waste of time to col­lect more data. Try­ing to get out of the gro­cery store in the fast­est way pos­sible seems to have more import­ant factors, such as the num­ber of jerks ahead of you in line.

As a side note on how that scat­ter­plot is presen­ted, it prob­ably would have made a lot more sense to meas­ure the time taken as a func­tion of how many items I bought, rather than the cash value of the items I bought. I’m far too lazy to count things, though.

So, from now on I’ll be decid­ing on self check­out versus nor­mal check­out based on how social I’m feel­ing. I sus­pect that means I’ll be using the self check­out a lot.

Originally published at Wizardlike research. You can comment here or there.