Question

Can someone explain the STANDARD DEVIATION OF THE DIFFERENCES formula to me?

Answer 1

@jagatuba @Jemurray3 @jhonyy9 @karatechopper @phi @robtobey @satellite73

Answer 2

http://www.google.com/imgres?um=1&hl=en&sa=N&biw=1440&bih=809&tbm=isch&tbnid=EWj_RcUArXWHWM:&imgrefurl=http://www.socialresearchmethods.net/kb/statdesc.php&docid=jsqc7fluc6WZ7M&imgurl=http://www.socialresearchmethods.net/kb/Assets/images/statdes3.gif&w=474&h=300&ei=q6aNUJK4C5S08ATpvoGACg&zoom=1&iact=rc&dur=392&sig=112477054274050808931&page=1&tbnh=124&tbnw=198&start=0&ndsp=21&ved=1t:429,r:0,s:0,i:71&tx=156&ty=39

Answer 3

I am given 2 sets of 10 numbers. How do I plug them into this formula to get the correct answer?

Answer 4

so what numbers you have got for ????

Answer 5

the sum across the values how you can get it ?

Answer 6

im confused about the top part of the formula. ive been getting the wrong answers so i must be doing something wrong.

Answer 7

sorry but this attachement i not can opening ,not id compatibly with my excell programm

Answer 8

what about now?

Answer 9

can you rewrite me here the values for x and X the mean or average and the value for n ?

Answer 10

@robtobey can you opening this attachement please ?

Answer 11

(column 1) x = 129, 237, 110, 32, 322, 134, 119, 32, 172, 149
total sum for x = 1436
mean for x = 143.6

(column 2) y = 130, 224, 113, 38, 320, 124, 122, 33, 169, 148
total sum for y = 1421
mean for y = 142.1

value for n = 10
df = n-1 (so 9)

Answer 12

have you any idea for this ?

Answer 13

yes but ive been getting the wrong answers.
d bar = 1.5

so ive been doing ((129-1.5)^2+(237-1.5)^2+(110-1.5)^2+.......))

Answer 14

so how i see it there will be in numerator sqrt(sum(x-X)^2)
divide by sqrt9 so divide by 3

ok ?

Answer 15

can you calcule first this sum ?

Answer 16

how many will be this sum ?

Answer 17

i got 270258.5 for x
and 261262.5 for y
then i subtracted the 2 to get 8996

Answer 18

then divide by 9 and square root it to get 31.616

Answer 19

but thats wrong

Answer 20

why divide by 9 and not by 3 ?

Answer 21

arent u supposed to do whats in the radical first and then square root it?

Answer 22

why you can separte it sqrt of numerator and sqrt of denominator and vide it after

Answer 23

and divide it after

Answer 24

i get the same answer either way

Answer 25

31.616

Answer 26

the right answer is 5.93

Answer 27

@jhonyy9

It may to late for solving this problem. Attached is a screen capture of part of the xls file.
I am running on a mid 2010 IMac with 8Gb of ram to support virtual versions of Windows XP pro, Windows 98SE and in the past Ubuntu Linux.

The xls file is not a normal spread sheet data file. All I can provide is a screen capture of what I see.

Answer 28

how can i opening it what program i need using for ?

Answer 29

i provided all the necessary info above ^^^^^

Answer 30

so than you need calcule right this sum and after make the squareroot of them ,yes ?

Answer 31

so and after just divide it by 3

Answer 32

Ask @mariomintchev what version of Excel did she/he use to generate the spread sheet.

Answer 33

Excel 2010

Answer 34

SCREENSHOT

Answer 35

They want the standard deviation of the differences.

Your formula tells you how to find the standard deviation of a list of numbers.

The first step is find the list of numbers: the list of differences
so find x-y
where
x= 129, 237, 110, 32, 322, 134, 119, 32, 172, 149
y = 130, 224, 113, 38, 320, 124, 122, 33, 169, 148

the differences (call it z) are
z= -1 13 -3 -6 2 10 -3 -1 3 1

now use your formula to find the standard deviation

Answer 36

so
((-1-1.5)^2+(13-1.5)^2+(-3-1.5)^2+....)) ???

Answer 37

yes, then divide by 9
then take the square root.

Answer 38

ok, i got 5.95 so its close enough. thanks phi, i can always rely on you!

Answer 39

I got 5.930


(dd-1.5).^2
6.2500 132.2500 20.2500 56.2500 0.2500 72.2500 20.2500 6.2500 2.2500 0.2500

sum(ans)/9 = 35.1667
sqrt(35.1667)= 5.9302

Answer 40

i must have made a little mistake somewhere when punching in all of those numbers and parenthesis. i understand what i need to do now though. thanks! =o)