The table shows the age distribution in years of a group of people
| Age(in years) | 1 - 5 | 6 - 10 | 11 - 15 | 16 - 20 | 21 - 25 | 26 - 30 |
| Number of people | 18 | 12 | 25 | 15 | 20 | 10 |
Using an assume mean of 13 years, find the mean age of the people.
Explanation
| Age | Class Mark(x) | Freq(f) | d = x - A | Fd |
| 1 - 5 | 3 | 18 | -10 | -180 |
| 6 - 10 | 8 | 12 | -5 | -60 |
| 11 - 15 | 13 | 25 | 0 | 0 |
| 16 - 20 | 18 | 15 | 5 | 75 |
| 21 - 25 | 23 | 20 | 10 | 200 |
| 26 - 30 | 28 | 10 | 15 | 150 |
| Total | | 100 | | 185 |
Where A is the assumed mean = 13
substituting, mean = 13 + \(\frac{18}{100}\) = 13 + 1.85
= 14.85 years
