Frequency Polygons Mastery

📊 What are Frequency Polygons?

A frequency polygon is a line graph that connects points representing the frequencies of different classes or intervals.

It's created by plotting the class-marks on the x-axis and their corresponding frequencies on the y-axis, then connecting these points with straight lines.

🔧 Key Properties

• Always starts and ends at zero frequency - This creates a closed polygon shape

• Area equals histogram area - The area under the polygon is mathematically equivalent to the histogram

• Great for comparisons - Multiple polygons can be overlaid to compare different datasets

• Smooth representation - Provides a continuous view of data distribution

📈 Construction Steps

Step 1: Prepare your data with class intervals and frequencies

Step 2: Calculate class-marks for each interval

Step 3: Add zero-frequency classes before and after your data

Step 4: Plot points (class-mark, frequency) on the graph

Step 5: Connect all points with straight lines

🎯 When to Use

• Comparing distributions - Multiple datasets on same graph

• Continuous data - When data represents continuous measurements

• Trend analysis - To see patterns and shapes in data

• Presentation - Clean, professional appearance for reports

• Statistical analysis - Foundation for more advanced statistical methods