| চল(\(x_i\)) | 10 | 15 | a | 25 | 35 |
| পরিসংখ্যা (\(f_i\)) | 3 | 10 | 25 | 7 | 5 |
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| চল \((x_i )\) | পরিসংখ্যা \((f_i )\) | \((x_i f_i)\) |
| 10 | 3 | 30 |
| 15 | 10 | 150 |
| \(a\) | 25 | \(25a\) |
| 25 | 7 | 175 |
| 35 | 5 | 175 |
| মোট | \(\sum f_i=50\) | \(\sum x_i f_i=530+25a\) |
∴প্রশ্নানুসারে,যৌগিক গড় \(=20.6\)
বা, \(\cfrac{\sum x_i f_i}{\sum f_i}=20.6\)
বা, \(\cfrac{530+25a}{50}=20.6\)
বা, \(530+25a=1030 \)
বা, \(25a=500 \)
বা, \(a=20\)