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Maths question.
Uni explaining how to figure out standard deviation.
Step 2: Square each difference. We want to know the overall deviation regardless of direction (− or +), but if we add the difference scores together, some will cancel each other out. Squaring the difference scores (multiplying each score by itself, e.g. −4 x −4) avoids this.
My question: Why can you not just ignore the +/- and thus erase both this step and the square root step later?
@alexisbushnell
Because if you did that then 5 +1 scores would have the same effect on it as 1 +5 score, and in the first case there is stronger correlation than in the second case, so you have to use squares to bias it towards greater outliers, so in the former the squares add up to 5, but in the latter it's 25.
@SmartmanApps oooooooh ok that makes sense, I think!
@alexisbushnell
Oh! If this wasn't clear the +1 is +1 above the mean, and +5 is +5 above the mean, as opposed to -1 and -5. i.e. we aren't just squaring to remove the negative, but also make the outlier scores have a bigger effect than those that are close to the mean
@alexisbushnell You can also do that. You get a different answer, called the 'mean absolute deviation' (or MAD). But the standard deviation is usually easier to work with. Thus is because, from the point of view of doing algebra, squaring is a simpler operation than taking the absolute value.
@OscarCunningham oh interesting, thank you so much, that's really helpful.
I'm not nearly enough of a statistician to answer your question, but I understand it.
Statistics get funky at the higher levels.
@Uair it makes no sense at all to me, even just from a logic level.
If you're doing something just to undo it later - why are you doing it at all?
Also not doing it gave me almost the same answer (2 for me vs 2.21 for them).
This is a bonfire demo instance for testing purposes
