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)'.
Multiply for Weighted Average. 1  1. Multiply each number by its weight. You can choose to write this at the end of the chart or to do it on 1 line, in a formula. 2  2. Add the weighted scores together. For example, 0.9(0.25) + 0.75(0.50) + 0.87(0.25). 3  3. Note that the weights should total 100 if you are using percentages.