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)'.
: (1) This idea can be generalized to allow the calculation of the weighted average of a continuous function. f.x/. Here the individual weights are replaced by a weighting functionw.x/, so that the âweightâ off.x/. at x is w.x/ dx. We also replace the summations in Eq. (1) with integrals; the weighted average off.x/is.