Pistachios OR One simple method to have a pretty weird grocery shopping experience

So for a long time I had been under the impression that I didn't really like pistachios.  Once - years ago - I had a bunch and then didn't feel great later on that evening.  The human mind has some great methods to create strong linkages between foods and feelin' bad, as back in a hunter gatherer stage such linkages would have been exceptionally useful.

In any case, I didn't really think much of it and just didn't really eat pistachios again.  It doesn't seem like I really came across them that much in day to day life, so it wasn't something that I really had to avoid.  

Recently, I was hanging out with some friends and they put out some pistachios, and I figured I'd give them a try.  Long story short, they're delicious.  Take that, hunter gatherer part of my brain.  

This was a few months ago, and I finally saw some bulk pistachios at the store last week.  I bought some, and realized that they're one of the few nuts that you can't buy without the shell (there are actually some good reasons for it, apparently).  You can certainly buy other nuts with their shells, but few of them really require it (with the exception of some of the more novel nuts, like hazelnuts).

Examining what I got from the store led to the conclusion that in any given scoop of pistachios you're getting mostly whole pistachios.  Aside from this, you're also getting some nuts that have come out of the shell and some shells that don't have nuts in them.  

I was curious about this, initially, and a cursory pass does seem to suggest this is noise that basically cancels out - you get about the same number of empty shells as you get shell-free nuts in any given pull.  In the aggregate, then, you're still basically getting whole nuts.

Continuing to think about this a little bit - while sitting around eating pistachios - a thought crossed my mind.  

What if you were really careful at the bulk bin?  Instead of taking indiscriminate scoops, why not try to be a bit more calculating?  If you could aim for already shelled nuts and avoid nut-free shells, you might save a little change (which you could use to buy more pistachios, duh).  

Now, the short answer to the longer question is that you don't do this because it would look really weird if you sat at the bulk bin picking out shells and shell-less nuts.  People would probably start to stare.  The extension would also be that at a certain point you should stop searching and just start shelling - take the good stuff to the scale and leave the shells behind.  

But how much is this really going to impact your total?  How much does a pistachio nut weigh in relation to a pistachio shell?

Easy enough - I have a kitchen scale for just these sorts of questions.  

The weight of one whole pistachio is...0 ounces.  

The weight of one pistachio shell is...presumably less than that.  

You see, my kitchen scale doesn't have the resolution to specify things at the level of a single pistachio, let alone a single shell.  This is not a problem only unique to my kitchen scale (or to pistachios).  

How to fix it?  Well, averages based on larger samples.  

10 pistachios give a measure on my scale, though the resolution is still not there to pick up small differences. In fact, 10 pistachios generally fluctuates between 1/8 and 1/4 of an ounce, meaning that the actual average weight it likely somewhere between those numbers.  My kitchen scale does not give values between those two numbers. 

Where between does that actual number fall?  Well, my scale can't tell me that, at least not exactly.  But if I take enough samples I can get a proportion that shows what amount of time the scale comes up 1/8 vs 1/4.
If we treat these as the likely bounds of the weight for 10 pistachios, then the proportion of the time the higher number comes up is the percent distance we have to travel between those two numbers.  

Put another way, we can take the average of those measures and find a point between them that is a best guess for the true weight of 10 pistachios.  

We can do the same for some sets of 20, even 40, and see if those help to give us a better picture of the scale (they do).  

At a certain point, it's simply time to eat some pistachios.  

I didn't weight the nuts themselves, as with the weight of the whole pistachio all we really need is the weight of the shell - the average weight of the nut should be what's missing.  It's also much harder to shell a pistachio and then just set the nut and shell aside, especially when you only need to set one aside to be able to figure out the weight of whatever you eat. 

The same idea of needing to use multiple shells on each measure holds, as the shells are lighter than the whole nut before shelling (obviously).  

All said and done, the weights come out as follows:

Whole nut: 0.042 ounces

Just shell: 0.019 ounces

Thus, just nut should be: 0.23 ounces

Interestingly, the weights of just the shell and just the nut are pretty close to each other.  This is a good sign - for every five empty shells you leave in the bin you should be able to take four shelled nuts away at basically an even weight trade.  

It really only makes sense to make the trade, as if you're just leaving shells to save money you'd have to do a lot to make a dent.  At $7.99 a pound, a single shell (without nut) is worth a little less than...1 cent?  What's a few cents going to buy you?

Since the nut and shell weigh about the same, it means that (at these prices) a full pistachio should run you just over 2 cents.  A pistachio nut runs just a bit over a cent.  So, the question of what a few cents will buy you is one or two whole pistachios (or roughly twice as many shelled pistachios). 

A single penny might not seem like much, but given the fact that the whole thing is only twice the price of the nut means you're looking at somewhere in the ballpark of 40-50% savings by removing the shell.  

For a single nut, this might not make much sense.  But remember, we're doing this in aggregate!  Who goes to the store and buys a single pistachio?  

The logical conclusion is that you should - just as some people do with sweet corn - stand at the store and peel back those pennies from your pistachios.  

Just don't blame me if you get kindly (or unkindly) escorted out of the store.