I'm trying to develop a data control chart and I can't find the function for
relative percent difference...I think it might be a nested function that I
need to use? I'm new to this aspect of excel so, please be kind. I have
found the formula
ABS (A-B)/A but I need a function for relative percent difference....how can
I chage the following formula into something that works in excel?

(a-b)/((a+b)/2)*100 = relative percent difference, where a is a data point
in colum A and b is a data point in colum B?

Thanks

1. Open Excel and select the cell where you want to display the result.
2. Type the formula: =ABS((A-B)/((A+B)/2))*100, replacing "A" and "B" with the cell references for your data points.
3. Press Enter to calculate the result.

That's it! You now have the relative percent difference between your two data points. Let me know if you have any other questions or if there's anything else I can help you with.

JIn an empty cell, just replace the a and b with the actual cell
references..and place an = sign in front.

e.g

=(A2-B2)/((A2+B2)/2)*100

where cell A2 contains your a data point and cell B2 contains your b
data point.


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"bnorris" wrote:
(a-b)/((a+b)/2)*100 = relative percent difference

No. I believe RPD is: abs(a-b) / ( (a+b)/2 ) * 100. See
http://en.wikipedia.org/wiki/Percent_difference .

In Excel, that can be written:

=ABS(A1-B1) / AVERAGE(A1,B1)

formatted as Percentage. Alternatively:

=2*ABS(A1-B1) / (A1 + B1)

again formatted as Percentage.


----- original message -----

"bnorris" wrote in message
...
I'm trying to develop a data control chart and I can't find the function
for
relative percent difference...I think it might be a nested function that I
need to use? I'm new to this aspect of excel so, please be kind. I have
found the formula
ABS (A-B)/A but I need a function for relative percent difference....how
can
I chage the following formula into something that works in excel?

(a-b)/((a+b)/2)*100 = relative percent difference, where a is a data
point
in colum A and b is a data point in colum B?

Thanks