Mathematics
Calculate the mean of the following frequency distribution.
| Class-interval | Frequency |
|---|---|
| 5 – 15 | 2 |
| 15 – 25 | 6 |
| 25 – 35 | 4 |
| 35 – 45 | 8 |
| 45 – 55 | 4 |
Measures of Central Tendency
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Answer
We construct the following table, taking assumed mean a = 30. Here, c (width of each class) = 10.
| Class-interval | Frequency (fi) | Class mark (yi) | ui = (yi - a)/c | fiui |
|---|---|---|---|---|
| 5 – 15 | 2 | 10 | -2 | -4 |
| 15 – 25 | 6 | 20 | -1 | -6 |
| 25 – 35 | 4 | a = 30 | 0 | 0 |
| 35 – 45 | 8 | 40 | 1 | 8 |
| 45 – 55 | 4 | 50 | 2 | 8 |
| Total | ∑ fi= 24 | ∑ fiui = 6 |
By formula,
Hence, mean of the frequency distribution is 32.5.
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