# Average the difference of 2 columns w/out a 3rd column

#### scrandal

##### Board Regular
I have two columns:

A B

1 10
2 9
3 8
4 7
5 6
6 5
7 4
8 3
9 2
10 1

I need a formula that takes the difference of the two columns (1-10, 2-9, etc.) and then finds the average for all of the differences. I don't want to have a third column with the differences and then take the average of those. Any help would be much appreciated.

Thanks,
Steve

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##### MrExcel MVP
=AVERAGE(A1:A10-B1:B10)

which needs to be confirmed with control+shift+enter, not just with enter.

#### dcardno

##### Well-known Member
The average of the differences will be equal to the difference of the averages, so
Code:
``=AVERAGE(A1:A10) - AVERAGE(B1:B10)``
will also work, as will the difference in the sums divided by the number of rows of data. The only advantage is that they are not array formulas, and so don't need to be confirmed with Crtl-Shift-Enter (and may be easier for some users to follow)...

#### scrandal

##### Board Regular
Thanks for the quick responses. I think my question has been answered.

#### scrandal

##### Board Regular

I have a similar question to the one I asked earlier in this post.

Once again I have an array of data starting in A1:

1
2
3
4
5
6
7
8
9
10

Starting in cell B3 I have the formula =sum(A1:A3). I have filled this down to cell B10. Below are the results (Starting in B3):

6
9
12
15
18
21
24
27

Then in A11 I take an average of B3:B10. Is there a way to do the calculation in A11 without first having to do the intermediate step of suming the cells in column B? Thanks.

#### Domenic

##### MrExcel MVP
Try...

=AVERAGE(SUBTOTAL(9,OFFSET(A1:A10,ROW(INDIRECT("1:"&ROWS(A1:A10)-2))-1,,3)))

...confirmed with CONTROL+SHIFT+ENTER, not just ENTER.

Hope this helps!

#### scrandal

##### Board Regular

That works perfectly. Thanks.

#### scrandal

##### Board Regular
Let's see if we can take this a step further. Below are my columns of data (Starting in A1):

A B C

1 5 25
2 7 24
3 9 23
4 11 22
5 13 21
6 15 20
7 17 19
8 19 18
9 21 17
10 23 16

Starting in column D3 I have the formula =Sum((.5*(A1:A4))+(.25*(B1:B4))+(.25*(C1:C4))). I have filled this formula down to D10. Then I take an average of D3:D10 and get 12.5. Is there a way to get the result of 12.5 without the intermediate step of the calculations in column D?

#### Domenic

##### MrExcel MVP
Shouldn't the average be 34.125? If this is correct, try...

=AVERAGE(MMULT(SUBTOTAL(9,OFFSET(A1:C10,ROW(INDIRECT("1:"&ROWS(A1:C10)-2))-1,{0,1,2},3,1))*{0.5,0.25,0.25},{1;1;1}))

or

=AVERAGE(MMULT(SUBTOTAL(9,OFFSET(A1:C10,ROW(INDIRECT("1:"&ROWS(A1:C10)-2))-1,COLUMN(A1:C10)-COLUMN(A1),3,1))*{0.5,0.25,0.25},TRANSPOSE(COLUMN(A1:C10)^0)))

Note that the second formula needs to be confirmed with CONTROL+SHIFT+ENTER, not just ENTER.

Hope this helps!

#### scrandal

##### Board Regular
Thanks for the quick response. My average was wrong, but I get 12.13. With this formula in D3 "=SUM((0.5*(A1:A3)),(0.25*(B1:B3)),(0.25*(C1:C3)))" and I drag it down to D10 I get these values:

D3=9.5
D4=10.25
D5=11
D6=11.75
D7=12.5
D8=13.25
D9=14
D10=14.75

When I take the average of them I get 12.13, any ideas?

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