CBSE Book Class 11 Psychology What is Statistics

UNIT 2

WHAT IS STATISTICS?

Researchers deal with a large amount of data and have to draw dependable conclusions on the basis of data collected for the purpose. Statistics help the researchers in making sense of the enormous amount of data. Let us first understand the term statistics. Technically “statistics” is that branch of mathematics which deals with numerical data. Researchers are interested in variables. Variables refer to some aspect of a person, an object or environment that can be measured and whose value can change from one observation to the other. Statistics deals with description, summarising and representation of data. The inferential statistics helps to draw conclusions from data. The process of measurement involves use of rules to assign a number to a specific observation of a variable. Psychologists use four levels of scales: Nominal, Ordinal, Interval, and Ratio. Nominal scale is at the lowest level and ratio the highest. In general higher we go up the scale type, more information is contained in the scale.

GRAPHICAL REPRESENTATION OF DATA

After collecting data, the next step is to organize the data to get a quick overview of the same. Graphical representation helps us in achieving this objective. It is a part of the descriptive statistics through which we organize and summarise the data. The outcome is visually presented that makes it easy to see pertinent features of the data. Such presentations are called graphs.

There are different kinds of graphs. However, here we shall consider only the Bar Diagram, the Frequency Polygon, and the Histogram. These graphs have much in common, especially the frequency polygon and histogram, though, they look different.

Basic Procedures

Graphed frequency distributions generally have two axes: horizontal and vertical. The horizontal axis is called X-axis or abscissa and the vertical axis the Y-axis or ordinate. It is customary to represent the independent variable on the X-axis and dependent variable on the Y-axis. The intersection of the two axes represents the origin or the zero point on the axis. However, if the initial score (or midpoint of the class interval) of a data to be represented on the graph is away from zero (e.g. midpoint 142 in table 1), we break the horizontal line (axis) to indicate that the portion of the scale is missing.

To make the graph look symmetrical and balanced, it is customary to keep the height of the distribution about three-quarters of the width (height 75 pc of the width). Some trial and error may be necessary to create graph suitable in size and convenient in scale. The graph should be given clear and suitable caption with figure number and labels on both the axes. The caption of a graph is written below the graph with a suitable figure number.

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