3 - 7, 8 - 12, 13 - 17, 18 - 22. Which of the following is/are true?
I. The class Interval is 4
II. The class boundaries are 2.5, 7.5, 12.5, 18.5, 22.5
III. The mid-marks are 5, 10, 15, and 20
A
I only
B
II only
C
III only
D
I and II only
E
I and III only
Verified Correct Answer: E.
Step-by-Step Mathematical Solution
Given the class intervals: \(3 - 7\), \(8 - 12\), \(13 - 17\), and \(18 - 22\):
The class interval is \(4\):
\(7 - 3 = 4 \quad \text{(True)}\)
Class boundaries are \(2.5, 7.5, 12.5, 18.5, 22.5\):
- Correct boundaries: \(2.5, 7.5, 12.5, 17.5, 22.5\) False.
Mid-marks are \(5, 10, 15, 20\):
\(\text{Mid-mark} = \frac{\text{Lower} + \text{Upper}}{2}\)
- \(3 - 7: 5\)
- \(8 - 12: 10\)
- \(13 - 17: 15\)
- \(18 - 22: 20\) True.
Source: Myschool Past Questions Archive (Record #42455)