3) Frequency Distribution (Curve):- Frequency distribution curves are like frequency polygons. In frequency distribution, instead of using straight line segments, a smooth curve is used to connect the points. The frequency curve for the above data is shown as:

Shape of Distribution Curves:- We have seen what a distribution curve looks like. There are four types of distribution curves. (i) Symmetrical or bell-shaped (ii) Moderately symmetrical or skew (ii) J-shaped and (iv) U-shaped. We shall only study the first two.

i) Symmetrical distribution:- As the name suggests, if the distribution is symmetrical, the curve rises gradually, reaches a maximum then falls equally gradually. The curve looks like a bell. This curve is symmetrical about the maximum frequency. For a perfectly symmetrical distribution, the mean, the mode and the median all coincide. This curve displays perfect symmetry, that is, its left half is the mirror image of the other right half. A bell-shaped or mound-shaped curve is also known as the normal curve, giving it special properties. This is an ideal situation and therefore, rarely found in practice.

ii) Moderately symmetrical or Skew:- The curve is symmetrical but only moderately. If it rises rapidly, reaches a maximum and then falls slowly, it is a called a positively skewed curve. If it rises slowly, reaches a maximum and then falls rapidly, it is called a "negatively skewed curve". For these curves; the mean, the median and the mode do not coincide. In much of the economic and social phenomenon, we come across such curves.

Index

3.1 Introduction
3.2 Comparison Between Tabular And Diagrammatic Presentation
3.3 Difference Between Diagrams And Graphs
3.4 General Principles Of Constructing Diagrams
3.5 Bar Diagrams
3.6 Pie Chart
3.7 Graphs
3.8 Box and Whiskers

Chapter 4