Chapter 3: Organisation of Data

Meaning of Organisation of Data

Once data is collected, it is usually in an unorganized, raw format known as raw data. Organisation of data refers to the arrangement of figures in such a form that comparison of the masses of similar data may be facilitated and further analysis may be possible. Classification is the basic step in organization.

Types of Variables

A variable is a characteristic that can take on different values. In statistics, variables are broadly classified into two categories:

1. Discrete Variables: These variables jump from one complete number to another. They do not take intermediate values. Examples include the number of children in a family, number of rooms in a house, and cars produced by a company.
2. Continuous Variables: These variables can take any fractional value within a specific range. Examples include height, weight, temperature, and income.

Frequency Distribution

A frequency distribution is a comprehensive way to classify data according to some measurable characteristics.

• Frequency: The number of times a particular observation occurs in the given data.
• Class Interval: The range into which data is grouped (e.g., 0-10, 10-20). The difference between the upper limit and the lower limit is the class size.

When constructing a frequency distribution, one can use:

1. Exclusive Method: The upper limit of one class is the lower limit of the next class (e.g., 10-20, 20-30). A value exactly equal to the upper limit is excluded from that class and included in the next.
2. Inclusive Method: The upper limit of one class does not overlap with the lower limit of the next class (e.g., 10-19, 20-29). Both limits are included in the class.

Competency-Based Questions

Multiple Choice Questions

Q1. The marks obtained by students in a test can be fractional (e.g., 85.5). Which type of variable is this? (a) Discrete variable (b) Continuous variable (c) Qualitative variable (d) None of the above

Answer: (b) Continuous variable

Analytical Questions

Q2. An investigator collected data on the ages of residents in a society. They classified the ages as 0-9, 10-19, 20-29, 30-39. (a) Identify the method of classification used here. (b) Convert this distribution into an exclusive series. What is the necessity of making such a conversion?

Answer: (a) The investigator used the Inclusive Method of classification. (b) To convert it to an exclusive series, we find the adjustment factor, which is half the difference between the lower limit of a class and the upper limit of the previous class (\( (10-9)/2 = 0.5 \)). We subtract 0.5 from lower limits and add 0.5 to upper limits:

• -0.5–9.5 (or realistically 0-9.5)
• 9.5–19.5
• 19.5–29.5
• 29.5–39.5

Such conversion is necessary when calculating certain statistical measures like median or mode, which require continuous class boundaries to find exact values using formulas.