# Variance.p & Variance.s & Variancea

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### #1 Ata.H.D

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Posted 08 July 2015 - 10:01 AM

hi

see this

if I want to calculate Var.P on CP400, what should I do ??

Edited by Ata.H.D, 08 July 2015 - 05:28 PM.

### #2 pan.gejt

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Posted 08 July 2015 - 05:27 PM

Before starting I do some math first. You can compute Var.P by using of 2 methods:

1. method

Var.P=Var.S*(n-1)/n, Var.S is computed by ClassPad (command variance)

2. method

Var.P = (sigmax), where sigmax means population standard deviation

similarly

Var.S = (sx)2 , where sx means sample standard deviation

------------------------------------------------------------------------------------------------------------

the 1st method is suitable for list calculation,

Var.P = variance(list1)*(dim(list1)-1)/dim(list1), the list1 is used

Var.S = variance = 27130, n=dim(list1)=5

Var.P = 27130*(5-1)/5

Var.P = 21704

the 2nd method is suitable for spreadsheet calculation, because the sigmax is calculated

sigmax = 26.0546, computed value

Var.P = sigmax2

Var.P =147.3232 = 21704

sx = 164.712, computed value

Var.S = sx2

Var.S =164.7122 = 27130

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### #3 Ata.H.D

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Posted 08 July 2015 - 05:38 PM

Before starting I do some math first. You can compute Var.P by using of 2 methods:

1. method

Var.P=Var.S*(n-1)/n, Var.S is computed by ClassPad (command variance)

2. method

Var.P = (sigmax), where sigmax means population standard deviation

similarly

Var.S = (sx)2 , where sx means sample standard deviation

------------------------------------------------------------------------------------------------------------

the 1st method is suitable for list calculation,

Var.P = variance(list1)*(dim(list1)-1)/dim(list1), the list1 is used

Var.S = variance = 27130, n=dim(list1)=5

Var.P = 27130*(5-1)/5

Var.P = 21704

the 2nd method is suitable for spreadsheet calculation, because the sigmax is calculated

sigmax = 26.0546, computed value

Var.P = sigmax2

Var.P =147.3232 = 21704

sx = 164.712, computed value

Var.S = sx2

Var.S =164.7122 = 27130

TanQ

but wich 1 is true??

Eg. I got these on exam!! what should I do??

### #4 pan.gejt

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Posted 08 July 2015 - 06:35 PM

Sorry, I don't understand what you mean : "but which 1 is true??"

Both methods of computation are correct.

Differences between Population and sample standard deviations

http://libweb.surrey...ter/page_18.htm

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### #5 pan.gejt

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Posted 10 July 2015 - 10:04 AM

It's interesting much cheaper Classwizz computes both values directly

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### #6 Ata.H.D

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Posted 10 July 2015 - 03:03 PM

It's interesting much cheaper Classwizz computes both values directly

OMG !!!!

hi

after e-mail , I got this

Edited by Ata.H.D, 13 July 2015 - 01:23 PM.

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