A weighted average assigns each data point a weight that reflects how much it should count toward the final result. You multiply each value by its weight, sum all of those products, then divide by the total of all weights.
A simple average divides the sum of values by the count, treating every item equally. A weighted average lets items with higher weights pull the result toward their values. When all weights are equal, both methods produce the same number.
Emily is finishing her semester. Her professor weights the course as: quizzes 20%, midterm 30%, final exam 50%. Her scores are 85, 78, and 92.
Emily's simple average would be (85+78+92)/3 = 85.0. Her weighted average is 86.40 because the final exam score of 92 carries half the grade weight, pulling the result upward. Her weak midterm score of 78 only contributes 30% of the total, so its drag on the average is limited.
Note: This calculator normalizes weights automatically. Entering 20, 30, and 50 produces the same result as entering 2, 3, and 5 or 0.20, 0.30, and 0.50.
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