#High School Stats Calculating Standard Deviation

20 messages · Page 1 of 1 (latest)

rose python
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I took a gap year after High school and I've spent the last year pretty much completely sedentary(mentally) and I've forgotten the majority of what I learned in stats I suspect, so I decided to go through a HS stats course on khanacademy. Can someone explain where I went wrong calculating this problem?
First:
((2-10)^2+(9-10)^2+(14-10)^2+(15-10)^2)/3
Second:
sqrt (quotient of sum of deviations[answer from step 1]).

Issue
I got like 23 something as the answer which isn't even close, I double checked with google sheets and used the functions to solve it for me and got the correct answer. I tried to ask chatgpt if it knew what I did wrong and it said my process was right and thought I made a typo during calculation to get 23. I copy pasted this string through googles calculator though, my guess is a PEMDAS error but I'd like to make sure my foundation on calculating stdev still stands before I just begin using sheets to solve it every time.

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rocky scaffoldBOT
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rigid nimbus
night adder
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4 pieces of data so you need to divide by 4 instead of 3

rigid nimbus
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shouldnt you divide by 4

night adder
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ye lol

rose python
rigid nimbus
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thats standard dev not standard variance
idk if thats a different thing or not, i just know how to calculate stdev

rose python
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im not sure now lowkey tho

rigid nimbus
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idk where n-1 comes from

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probably something else, but unrelated when it comes to stdev

night adder
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to be honest ive seen the formula what you talking about OP in many textbooks, but ive always used the divide by N one which is population one

rose python
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I asked chatgpt again guys I think it might be a pemdas error but I'm not too sure.

I recalculated the variance with n instead of n-1 and got an answer closer to the actual answer, 5.14 opposed to 5.94, but I don't believe that was the error given their difference

Chatgpt seems to have done the same steps I did but it did them seperately, which makes me think the only difference would be pemdas

night adder
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honestly i dont think you did anything wrong tho. usually write it as one big expression but yeah. since this is sample, we should be dividing by N - 1 technically and it should be the right answer

rose python
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eh, well I guess that solves the problem. Ty everyone

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+close