Presentation of Data | Class 11 Economics Notes

FREQUENCY DIAGRAMS: HISTOGRAM, FREQUENCY POLYGON, FREQUENCY CURVE AND OGIVE

Frequency diagrams graphically represent grouped frequency distributions, especially for continuous data. The main types are histograms, frequency polygons, frequency curves, and ogives. A histogram consists of adjacent rectangles where the base represents class intervals and the area (or height if intervals are equal) represents frequency. If class intervals vary, frequency density (frequency divided by class width) is used for height. Histograms differ from bar diagrams in that bars are adjacent with no gaps, and width is meaningful. The mode of the distribution can be identified graphically from the histogram. A frequency polygon is formed by joining the midpoints of the tops of histogram bars with straight lines, extending to zero frequency at both ends. It is useful for comparing multiple distributions. A frequency curve is a smooth curve drawn through the points of the frequency polygon. An ogive is a cumulative frequency curve, with two types: 'less than' and 'more than' ogives, plotted against class limits. The intersection of these ogives gives the median of the distribution. These diagrams help in understanding the shape, central tendency, and spread of data distributions.

📊 Diagram: See figure_10: Histogram for daily wage earners; figure_11: Frequency polygon for same data; figure_12: Frequency curve; figure_13 and figure_14: 'Less than' and 'More than' ogives for marks data; table_8 and table_9: Corresponding data tables.

🔗 Connection: The next section discusses arithmetic line graphs for time series data.

Table on page 11 (16×2)

Table on page 15 (9×6)