mean and standard deviation | Revision Server | Page 1

molten birch Dec 18, 2022, 8:10 AM

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<@&791435371564892232>

molten birch Dec 18, 2022, 9:26 AM

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<@&791435371564892232>

wintry panther Dec 18, 2022, 9:28 AM

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well

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find the variance first

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then multiply it by n i think

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because variance is the sum of (x-xmean)^2/n for n=1 to n=150

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@molten birch

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@molten birch

molten birch Dec 18, 2022, 9:29 AM

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wait

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lemme send u

wintry panther Dec 18, 2022, 9:30 AM

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what

molten birch Dec 18, 2022, 9:30 AM

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wintry panther Dec 18, 2022, 9:30 AM

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what is d

molten birch Dec 18, 2022, 9:30 AM

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this is mark scheme

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im trying to equal the s.d to find it

molten birch Dec 18, 2022, 9:30 AM

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wintry panther what is d

its just me letting x - mean = d

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easier for me to visualise

wintry panther Dec 18, 2022, 9:31 AM

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thats confusing imo

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just find the variance (sd squared)

molten birch Dec 18, 2022, 9:31 AM

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but idk whats wrong with this

wintry panther Dec 18, 2022, 9:31 AM

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removes the sqrt problem

molten birch Dec 18, 2022, 9:31 AM

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yeah got it

wintry panther Dec 18, 2022, 9:31 AM

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so r u good now?

molten birch Dec 18, 2022, 9:31 AM

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wintry panther Dec 18, 2022, 9:31 AM

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yep

molten birch Dec 18, 2022, 9:32 AM

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but i do not get 5514

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is my mean on the right wrong

wintry panther Dec 18, 2022, 9:32 AM

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why did it go from 4.3 to 8.6

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variance = 8287.5/150 - 4.3^2

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variance x 150 = what u want

molten birch Dec 18, 2022, 9:33 AM

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is both mean supposed to be 4.3

wintry panther Dec 18, 2022, 9:33 AM

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yea

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molten birch Dec 18, 2022, 9:34 AM

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where did the - 4.3^2 go

wintry panther Dec 18, 2022, 9:34 AM

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its there

molten birch Dec 18, 2022, 9:34 AM

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on the right

wintry panther Dec 18, 2022, 9:34 AM

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it shouldnt be there

molten birch Dec 18, 2022, 9:34 AM

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what

wintry panther Dec 18, 2022, 9:34 AM

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because those two r mathematically equivalent

molten birch Dec 18, 2022, 9:34 AM

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wintry panther Dec 18, 2022, 9:35 AM

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why is there a second 4.3?

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on the right

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what are you computing on the right

molten birch Dec 18, 2022, 9:35 AM

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coz thats the mean

wintry panther Dec 18, 2022, 9:35 AM

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yes but u already took the meean away

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why7 r u doing it twice

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molten birch Dec 18, 2022, 9:36 AM

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coz im trying to equal both variance

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u need to minus mean^2

wintry panther Dec 18, 2022, 9:37 AM

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those r both variance anyways

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u dont need to subtract mean^2

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variance is the mean of the squares subtract the mean squared (what u did on the left)

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or just the formula on the right

molten birch Dec 18, 2022, 9:38 AM

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i dont understand

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i did the same for other questions and got correct

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for example

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@wintry panther

wintry panther Dec 18, 2022, 9:46 AM

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thats fifferent

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thats coded data

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other data wasn't coded

molten birch Dec 18, 2022, 9:48 AM

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?

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i just dont understand why does the mean just disappear

wintry panther Dec 18, 2022, 9:53 AM

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because the mean isnt in that formula

molten birch Dec 18, 2022, 9:53 AM

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variance formula is

wintry panther Dec 18, 2022, 9:53 AM

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send what formula u are using

molten birch Dec 18, 2022, 9:53 AM

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square/frequency - mean^2

wintry panther Dec 18, 2022, 9:54 AM

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yes

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https://cdn.discordapp.com/attachments/1053942020277817354/1053968600559529994/image0.jpg

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thats the bit on the left

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what are u using for the right ?

molten birch Dec 18, 2022, 9:55 AM

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wintry panther Dec 18, 2022, 9:55 AM

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once again

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thats the one on the left

molten birch Dec 18, 2022, 9:55 AM

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yeah

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what about the right

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where did the mean go

wintry panther Dec 18, 2022, 9:55 AM

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what formula is that?

molten birch Dec 18, 2022, 9:55 AM

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standard deviation

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whats the other formula

wintry panther Dec 18, 2022, 9:56 AM

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thats sd

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the bit in blue

#mean and standard deviation