Question
What is a graph? Explain.

Answer

Graph:
  • A pictorial representation of observed data is called a graph.
  • A graph is drawn for statistical information which is not self-explanatory. In other words, the graph can neither be created nor be understood by people who do not have thorough knowledge of statistics.
  • A graph is drawn for data having continuous frequency distribution. For example,
    1. Classification of people into various groups based on their incomes
    2. Division of students on the basis of their marks, etc.
Example of continuous data:
Income of people per month $($in $Rs.)$ Number of people earning the income $($Frequency$)$
$10,000 – 20,000$ $500$
$20,000 – 30,000$ $300$
$50,000 – 1,00,000$ $100$
Price $($In $Rs.)$ Demand $($in units Frequency$)$
$1$ $100$
$2$ $80$
$5$ $70$
$7$ $20$
$10$ $10$
Generally, continuous data is bigger in size and complex in nature. Hence, statistical tools are used to analyze, classify and simplify it.
  • A graph is generally drawn on a graph paper. A graph can extend over one or more of the four quadrants obtained by the intersection of $‘X’$ and $‘Y’$ axis on a plane. Moreover, it cannot be drawn without taking appropriate measurements.
  • Graphs are used more by researchers and in higher education.
  • Graphs are not used or published for general public. They are created by researchers for their data analysis and understanding purposes only.
Types of graphs:
Important graphs used in economic study are:
  1. Time-series graphs
  2. Graphs for continuous frequency distribution
    • Histogram
    • Frequency polygon
    • Frequency curve
    • Cumulative frequency polygon
  3. Graphs for logarithmic data

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