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 Find the average weekly hours with the equation (30 + 25 + 35 + 40) / 4 = 32.5. 2  If you earn $19 per hour, then calculate your annual salary with the equation (32.5 x $19) x 52 = $32,110. 3  Keep track of your weekly hours with spreadsheet software or a time-tracking app.