Frequency Polygon X-Axis

In a frequency polygon, frequencies are always plotted against:

Correct Answer Explanation

In a frequency polygon, frequencies (as ordinates) are always plotted against the mid-points of class intervals.

Key Points:

• Both class boundaries and class-marks (mid-points) can be shown on X-axis.
• But frequencies are always plotted at the mid-point regardless.
• The distances between consecutive class marks should be proportional to class interval width.
• Points are joined by short straight lines to form the polygon.

Why Other Options Are Wrong

• A. Upper class limits: These are used for "less than" ogive.
• B. Lower class limits: These are used for "more than" ogive.
• D. Class width: Class width is not plotted on any axis.