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 Wednesday, July 28, 1999 #2666

How are weighted averages calculated?
 The Media Guru Answers(Saturday, July 31, 1999 ):

Each value in a series is multiplied by its appropriate weight and the sum of the products is divided by the sum of the weights. Example:
 The ratings of a TV program are 5.0 for teens, 4.0 for Adults 1824 and 3.0 for Adults 2549, so what is the 1249 rating?
 It's not the straight average of 5.0, 4.0 and 3.0, or 4.0; we must account for the different sizes of the populations in these three age groups.
 Let's suppose the teen population is 22.5 million, A1824 is 24.7 million and A2549 is 103.3 million. We multiply each rating by its population base:
5.0 x 22.5 = 112.5 4.0 x 24.7 = 98.8 and 3.0 x 103.3 = 309.9  Sum the products: 112.5 + 98.8 + 309.9 = 521.2
 Sum the weights:
22.5 + 24.7 + 103.3 = 150.5  Divide the sum of products by the sum of weights
521.2 ÷ 103.3 = 3.5 correct (weighted) average rating.
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