| Class Interval | 0-20 | 20-40 | 40-60 | 60-80 | 80-100 |
|---|---|---|---|---|---|
| Number of Students | 15 | 18 | 21 | 29 | 17 |
The modal class is the class with the highest frequency.
In the table, the class intervals are 0-20, 20-40, 40-60, 60-80, and 80-100.
The corresponding frequencies (number of students) are 15, 18, 21, 29, and 17.
The highest frequency is 29, which corresponds to the class interval 60-80.
Therefore, the modal class is 60-80.
| Number of students per Teacher | Number of Schools |
| 20 - 25 | 5 |
| 25 - 30 | 15 |
| 30 - 35 | 25 |
| 35 - 40 | 30 |
| 40 - 45 | 15 |
| 45 - 50 | 10 |
| Number of students per Teacher | Number of Schools |
| 20 - 25 | 5 |
| 25 - 30 | 15 |
| 30 - 35 | 25 |
| 35 - 40 | 30 |
| 40 - 45 | 15 |
| 45 - 50 | 10 |
| x | 5 | 10 | 15 | 20 | 25 |
| f | 6 | 8 | 6 | y | 5 |
| x | Less than 10 | Less than 20 | Less than 30 | Less than 40 | Less than 50 | Less than 60 |
| f | 3 | 12 | 27 | 57 | 75 | 80 |
If the variance of the frequency distribution
| xi | Frequency ft |
| 2 | 3 |
| 3 | 6 |
| 4 | 16 |
| 5 | \(\alpha\) |
| 6 | 9 |
| 7 | 5 |
| 8 | 6 |
is 3 , then $\alpha$ is equal to