I’ve always thought this kind of funny: even people who are “bad at math” tend to have a good handle on order of operations. You know: do the exponents first, then multiplication and division, and then addition and subtraction.
It turns out that Excel violates that standard in one way. Like all things with computers though, our lack of clarity about what we’re doing is part of the problem: GIGO.
So, consider the following:
You and I look at this and say: “three minus five equals minus two”. That’s correct, but it misses an important subtlety: the two occurrences of minus in that phrase are homophones — they sound the same but have different meanings!
A better way to state that equation would be “three subtract five equals negative two”. That’s correct because subtraction requires you to know both numbers, while negation only requires you to use one.
So, what does Excel do? In order of operations, most people lump negation together with subtraction. Excel does not: it does negation before even exponents.
This can very easily make a difference in your Excel calculations. Consider this
If you evaluated this by hand, you’d do the exponent before the minus, like so:
-3^2 = -(3^2) = –9
But, not Excel. Excel says that it makes a difference whether that minus is used for subtraction or negation: subtraction would go after exponentiation, but negation would go before exponentiation. So, Excel does it this way:
-3^2 = (-3)^2 = 9
Wow. There’s got to be a world of hurt in the business world from that one.
Two thoughts about this visualization of Domino’s delivery routes:
1) The bicycle deliverer is a piker. I delivered (by car) in the Buffalo suburbs for over 4 years. I covered about 100 square miles of territory, did over 100 miles of stop-and-go-driving on a weekend night, and the suburbanized swampy terrain had very few neat, homogenous rectangles.
2) What a great video for the transshipment portion of a linear programming or Excel class.
P.S. We have a distribution center (one of the red nodes towards the video’s end) for Wal-Mart located about 35 miles south of my home. I recently found out that it’s actually a distribution center for distribution centers: it handles mostly clothing, and ships nothing directly to stores.
I am going through this with a co-author right now. His vision was to use raw data put out by the NHL. My reality was that this data was over 1,000 observations on over 1,200 games. I went with the script:
Now that it’s done (thanks to Trevor MacDonald) I know I am way out on the right of this chart.
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