For the scores 1, 2, 1, 4, what is the value of Σ(X − 1)?

For the scores 1, 2, 1, 4, what is the value of Σ(X − 1)?

• A. 4
• B. 6
• C. 8
• D. 10

Answer: (A)

This asks you to sum deviations from 1: add up how far each score is from 1. Subtract 1 from each score: 1−1 = 0, 2−1 = 1, 1−1 = 0, 4−1 = 3. Then add these results: 0 + 1 + 0 + 3 = 4. You can also see it by the algebra rule Σ(X−1) = ΣX − n·1. Here ΣX = 1 + 2 + 1 + 4 = 8 and n = 4, so 8 − 4 = 4. The value is 4.

This asks you to sum deviations from 1: add up how far each score is from 1. Subtract 1 from each score: 1−1 = 0, 2−1 = 1, 1−1 = 0, 4−1 = 3. Then add these results: 0 + 1 + 0 + 3 = 4. You can also see it by the algebra rule Σ(X−1) = ΣX − n·1. Here ΣX = 1 + 2 + 1 + 4 = 8 and n = 4, so 8 − 4 = 4. The value is 4.