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From: Tommy on 18 May 2010 15:35
Can someone explain mathematically why the difference of the sum of the
average of row two and three (Range D2:D3) as shown in cell E3 is different
than the average of each individual difference in range A4:C4 as shown in
cell E4.
It is not obvious to me.

test 1 test 2 test 3 Average Diff
10 5 10 8,33
6 1 2 3 -64,00 %
-40,00 % -80,00 % -80,00 % -66,67 %

--
Regards
Tommy
From: Reeza on 18 May 2010 15:47
On May 18, 12:35 pm, Tommy <To...(a)discussions.microsoft.com> wrote:
> Can someone explain mathematically why the difference of the sum of the
> average of row two and three (Range D2:D3) as shown in cell E3 is different
> than the average of each individual difference in range A4:C4 as shown in
> cell E4.
> It is not obvious to me.
>
> test 1  test 2  test 3  Average Diff
> 10      5       10      8,33    
> 6       1       2       3       -64,00 %
> -40,00 %        -80,00 %        -80,00 %                -66,67 %
>
> --
> Regards
> Tommy

Weighted Average vs Average
Test 2 is 5 not 10 like the others, but in percentage points they
all become the same scale or same weights. Change Test 2 to 10 and 2
and you should get the same numbers or calculate a weighted average
rather than average...depends on what you're looking for at the end of
the day.

HTH,
Reeza
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