# When to Use Weighted Averages ••• Goodshoot/Goodshoot/Getty Images

An average is a measure of the center of a data set. You calculate the average by adding together all the data points and dividing by the total number of data points. Each number counts equally in the calculation. In a weighted average, some numbers count more than others or carry more weight, so use a weighted average whenever some data points are worth more than others. ••• Thinkstock/Comstock/Getty Images

Weighted averages are frequently used when calculating a final grade for a specific course, as the final comprehensive exam usually counts more toward the course grade than each of the chapter tests. If you did poorly on the three chapter tests, getting grades of 50 percent, 50 percent and 40 percent but you aced the final at 97 percent, your average will only be 59.25 percent if all the tests counted equally -- the sum of the total scores, 237 divided by the number of tests, 4. If your teacher told you that the final exam was worth as much as the chapter tests, you would assign a weight of 3 to the final and a weight of one to each of the chapter tests. Multiply each test score by its weight, to obtain, 50, 50, 40 and 291. The sum of the weights is 431 divided by the total number of points, 6. Your weighted average would be 71.83 percent, a much higher score.

## Calculating Batting Average ••• Jupiterimages/Brand X Pictures/Getty Images

When calculating batting averages in baseball, a weighted average is typically used, with each type of hit carrying a different weight. A player was at bat a total of 28 times and he struck out 5 times and hit 4 singles, 5 doubles, 6 triples and 8 home runs. Each of these results carries a different weight, a no-hitter=0, a single=1, a double=2, a triple=3 and a home run=4. His weighted batting average is the sum of each of these hits types multiplied by their respective weights, or 64, divided by the total number of times at bat, or 28. This player's weighted batting average is, therefore 2.29.

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