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Frequency Polygon

Frequency Polygon. Frequency Polygon. A frequency polygon is a line graph in which points are joined by straight lines and closed to make a polygon A frequency Polygon indicates the spread and skewness of distribution. Drawing Frequency Polygon.

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Frequency Polygon

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  1. Frequency Polygon

  2. Frequency Polygon • A frequency polygon is a line graph in which points are joined by straight lines and closed to make a polygon • A frequency Polygon indicates the spread and skewness of distribution.

  3. Drawing Frequency Polygon • A frequency polygon is drawn by plotting the frequency (or frequency density) against the midpoints of the data. • It can be superimposed on a histogram by connecting consecutive midpoints of the tops of columns • The area under the polygon represents the frequency of the data ( and is the same as the area of all the bars in the histogram)

  4. Example 1

  5. Example 1

  6. Example 1

  7. Example 2

  8. Example 2

  9. Drawing Frequency Polygon • More Examples for you to try:

  10. Analyzing Frequency Polygon • When the sample is large and there is a large number of intervals, since there are a large number of line segments the frequency polygon approaches FREQUENCY CURVE. • The Frequency Curve (or the Polygon) indicates the spread/dispersion of the distribution. Low Dispersion High Dispersion

  11. Analyzing Frequency Polygon • A Frequency Curve (or the Polygon) also indicates the SKEWNESS (“lopsidedness”) of the distribution. • Normal Curve (symmetric) • Examples Weight, Height, IQ Test scores

  12. Analyzing Frequency Polygon • A Frequency Curve (or the Polygon) also indicates the SKEWNESS (“lopsidedness”) of the distribution. • Positively Skewed Distribution • Examples Number of children in a family Age at which women marry Distribution of wages in a firm Positive side stretched

  13. Analyzing Frequency Polygon • A Frequency Curve (or the Polygon) also indicates the SKEWNESS (“lopsidedness”) of the distribution. • Negatively Skewed Distribution • Examples Daily maximum temperatures for a month in summer Reaction times for a experiment Negative side stretched

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