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Frequency polygon is a closed figure got by joining the Middle points of the top of rectangles of histograms.

It consists of a number of rectangles, those are vertically adjacent. Class intervals are taken on X-axis and frequencies on Y-axis. Rectangles are formed of the height proportionate to their frequencies.

A graph refers to the plotting of different valves of the variables on a graph paper which gives the movement or a change in the variable over a period of time.

Although tabulation is very good technique to present the data, but diagrams are an advanced technique to represent data.

What are the Merits and Demerits of Rank Difference Co-efficient of Correlation?

What are the Merits and Demerits of Scatter Diagram?

The measures of Central Tendency and Dispersion are used to compare two or more series. But it is not the comparison that is always wanted.

The objects of Descriptive Statistics are mainly – condensation by frequency distribution, and description of the frequency distribution by suitable statistical measures.

It is the form of a curve which is derived from the cumulative percentage of the given variables. This curve was given by Dr. Max O. Lorenz a popular Economic- Statistician. He studied distribution of Wealth and Income with its help.

The idea of Standard Deviation was first presented by Karl Pearson in 1893. This measure is widely used for studying dispersion.

Mean deviation is a measure that removes several shortcomings of other measures i.e. it does not ignore extreme terms or values which play a significant role in average or Mean.

Absolute measures of Dispersion are expressed in same units in which original data is presented but these measures cannot be used to compare the variations between the two series.

So going through the merits and demerits, we conclude that Quartile Deviation cannot be relied on blindly.

Merits and Demerits of Range…

Literally, dispersion means deviation, difference or spread of certain values from their central value. In relation to statistical seris, it means, deviations of various items of the series from its ventral value.

The use or application of a particular average depends upon the purpose of the investigation. Some of the cases of different averages are as follows: