In any statistical enquiry, at the outset, data are collected. Such data are to be condensed to make them fit for analysis and interpretation. Classification is the first step of condensation. There are various types of classification such as chronological, spatial, qualitative and quantitative.
After classification, data are to be presented. There are mainly two methods of presentation of data-Tabular presentation, Graphic and diagrammatic presentation.
Tabulation is a method of arranging data systematically in rows and columns. There are various parts of a table, such as, title, table number, heading, head note, caption, stub, body, foot note and source note.
There are different types of table such as general purpose table, & special purpose table; simple table and complex table.
Diagrams and graphs are the pictorial devices used for presenting statistical data in a summary form. Important diagrams used in statistical analysis are-bar chart (simple, multiple and component); area diagrams like, circle, square, pie chart, cartography and pictographs.
Graphs are more useful than diagrams in statistical analysis. They show functional relation between two variables. There are two types of graphs-time series graph and frequency graph. Time series graph represents a time series on a graph paper. It is used to compare a quantitative phenomenon over time.
Frequency distributions are represented by frequency graphs. Frequency distribution is a table which shows the different values of a variable and their respective frequencies. There are mainly two types of frequency distribution (or frequency array). These are discrete frequency distribution and continuous frequency distribution, On the basis of a given data set, we can construct frequency distributions. Continuous frequency distribution may be exclusive type, inclusive type or having open-ends.
There are various types of frequency graph. Most important ones are histogram, frequency polygon, frequency curve, and cumulative frequency curves (or Ogives). Diagrams and graphs are fascinating to eyes. They produce lasting impression in the mind of the readers than tables. However, diagrams and graphs have some limitations.