Wieghted average

[rsoper]

Sorry by re-posting twice, I was not sure how to add additonal inforamtion to my first cry for help.

I have included the text from first request and added addtional text..

I have a table that calculates on time delivery.

Values are:
Items delivered Items delivered on time OTD
A B =1-(A-B)/B
There are many items in this file.
.
.
I am interested in creating a value for weighted average, where a row with more items delivered would have a higher impact on the total weighted average than items with less delivered.
.
.
I am struggling on the formula, please help.
To give more information.

Example
Items Items
Ordered On-time" Formula
1364 1223 89.66%
937 800 85.38%
879 777 88.40%
703 669 95.16%
28 9 32.14%
18 5 27.78%
1 0 0.00%
13 0 0.00%
Total Item
3943 3483 52.32% Average

As I stated the Formula is = 1 - (A-B)/A

This value gives "on-time" %. But look at the numbers when averaging the formula column. 52.32% is the correct average, but it is being skewed by the last 4 items with low %'s. I want to make a value that considers the fact that the first 4 items had many more items thus should have a higher weighting making the weighted average closer to 80% area.
"weighted average".

Thanks for your help.

 

[Barrie Davidson]

Why not try the formula on your totals? IE, 3483/3943 which is 88.3%.