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Question
Calculate Mean deviation about Mean of the following data.
| X | 2 | 5 | 6 | 8 | 10 | 12 |
| f | 2 | 8 | 10 | 7 | 8 | 5 |
Solution
| X | f | fX | |D| = |X − 7.5| | f|D| |
| 2 | 2 | 4 | 5.5 | 11 |
| 5 | 8 | 40 | 2.5 | 22 |
| 6 | 10 | 60 | 1.5 | 15 |
| 8 | 7 | 56 | 0.5 | 3.5 |
| 10 | 8 | 80 | 2.5 | 20 |
| 12 | 5 | 60 | 4.5 | 22.5 |
| N = 40 | ∑fX = 300 | ∑f|D| = 94 |
Mean = `(sum "fX")/"N" = 300/40` = 7.5
∴ Mean deviation about mean = `(sum "f"|"D"|)/"N" = 94/40` = 2.35
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