Some purchasing specialist jobs also assign specialists to track the maintenance of office equipment. Maintaining records of warranties and service agreements is sometimes expected of a person in this position.
A retail price index would take this into account and use a weighted average which gives more prominence to commonly bought items. Excel does not contain a built in function to calculate a weighted average. It is however easy to do it using the SUMPRODUCT() function in a simple formula. SumProduct() multiplies two arrays (or ranges) together and returns the sum of the product. In the illustration it would calculate '(B4 x C4) + (B5 x C5) + (B6 x C6)'.
To find a weighted average, follow these steps: In a new worksheet, type the following data: A1: Cost B1: Cases. A2: $.20 B2: 10. A3: $.30 B3: 40. Type the formula below in any blank cell (it is not necessary to type this formula as an array): =SUMPRODUCT(A2:A3,B2:B3)/SUM(B2:B3)