Meaning: A continuous series is data arranged in class intervals, such as 0–10, 10–20 and 20–30.
To calculate its mean, we first find the midpoint of each class interval.
Formula:
Here:
- \(f\) = Frequency
- \(m\) = Midpoint of the class interval
- \(fm\) = Frequency × Midpoint
Step 1: Prepare the table.
| Class interval | Midpoint (m) | f | fm |
|---|---|---|---|
| 0–10 | 5 | 5 | 25 |
| 10–20 | 15 | 15 | 225 |
| 20–30 | 25 | 20 | 500 |
| 30–40 | 35 | 25 | 875 |
| 40–50 | 45 | 20 | 900 |
| 50–60 | 55 | 15 | 825 |
| 60–70 | 65 | 5 | 325 |
| Total | 105 | 3675 |
Step 2: Find the total frequency.
Step 3: Find the total of fm.
Step 4: Calculate the mean.
Final Answer: 35.0
Remember for exams:
- Find the midpoint of each class interval.
- Multiply each midpoint by its frequency.
- Add all frequencies and all \(fm\) values.
- Divide total \(fm\) by total frequency.
