[Math] How to compute the percentage of difference between two values

percentages

If there are two real values called week1val and week2val, what operation is required to calculate the percentage of difference between the two values? Does the higher of the two values need to be used for calculation, the lower of the two, or what?

For example, with these particular values:

week1val = 2.77
week2val = 2.84
diff = (week2val - week1 val) // (0.07)

…how is the percentage of difference between the two values computed? Is it like so:

pct = diff div [the larger of week1val and week2val] // In the contrived case: "0.07 div 2.84"

…or:

pct = diff div [the smaller of week1val and week2val] // In the contrived case: "0.07 div 2.77"

…or some other way???

Best Answer

It is entirely context dependent. You're choosing what you want to use as a "baseline" option.

  • If you're looking at something year by year, you will often compare to the older year.
  • If you're comparing a statistic and a population's mean, you'll compare to the population mean.
  • If you're looking to compare two individual data points where you can't differentiate them in another way, you arbitrarily use one as the baseline and compare the other to it.

That being said, anecdotally, I'm marginally more accustomed to seeing the smaller value used as the baseline, but that may even be related to fields of study and places of employment.

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