Data – Its Source and Compilation — NCERT Solutions

A foot note in a table gives extra information or clarification about the data in the table, such as a special condition, exception, or explanation of symbols. It helps the reader understand the table correctly.

Primary sources of data are those from which data are collected for the first time by an individual, a group, or an institution. Examples include personal observations, interviews, questionnaires/schedules and direct field measurements.

Five sources of secondary data are: government publications, semi/quasi-government publications, international publications, private publications, and newspapers and magazines. The chapter also mentions electronic media and unpublished sources.

Secondary data may be collected from both national and international agencies. National sources include government publications such as the Census of India, reports of the National Sample Survey, Weather Reports of the Indian Meteorological Department, Statistical Abstracts of state governments, and reports of various commissions. International sources include publications of United Nations agencies such as UNESCO, UNDP, WHO and FAO. Their important publications include the Demographic Year Book, Statistical Year Book and the Human Development Report.

An index number is important because it shows changes in a variable or a group of related variables over time and also helps compare different places, industries or countries. It is widely used to study changes in price and quantity.

For example, in the chapter the production of iron ore in India is taken with 1970–71 as the base year.

• Base year production = $32.5$ million tonnes
• 1980–81 production = $42.2$ million tonnes
• 1990–91 production = $53.7$ million tonnes
• 2000–01 production = $67.4$ million tonnes

Index number is calculated by:

$$\frac{\sum q_i}{\sum q_0} \times 100$$

So:

• 1970–71: $\frac{32.5}{32.5}\times 100 = 100$
• 1980–81: $\frac{42.2}{32.5}\times 100 \approx 130$
• 1990–91: $\frac{53.7}{32.5}\times 100 \approx 165$
• 2000–01: $\frac{67.4}{32.5}\times 100 \approx 207$

This shows that iron ore production increased from 100 in the base year to 207 in 2000–01.

Using the inclusive method, the marks can be grouped into classes of width 1:

Grouped frequency distribution in class intervals of 2:

So the data may be represented in grouped form as above.