Data: Its Source and Compilation, Class 12 Practical Geography

What Data – Its Source and Compilation is about

Key concepts

What data are and why geography needs them

NCERT section What is Data?; Need of Data; Presentation of the Data

• Data: numbers representing real-world measurements; datum = one measurement.
• Information: what we get after deriving, deducing or calculating from many data; a meaningful answer to a query.
• Need: many phenomena on the earth's surface are interrelated and are best explained quantitatively. To study a cropping pattern, you need cropped area, yield, production, irrigated area, rainfall and inputs like fertilisers and pesticides. To study a city's growth, you need population, density, migrants, occupations, incomes, industries, transport and communication.
• Shift in geography: from qualitative description to quantitative analysis, using precise techniques from collection and compilation to tabulation, ordering, analysis and conclusions.
• Statistical fallacy: NCERT's story of a man who measured a river at four points (0.6, 0.8, 0.9 and 1.5 m), found an average of 0.95 m, and led his family across because his child was 1 m tall; the child drowned at the deep point. An average can hide extremes, so how data are presented and interpreted matters as much as collecting them.

Primary sources of data

NCERT section Sources of Primary Data

Primary data are collected for the first time by an individual, a group or an organisation.

1. Personal observation: direct observation in the field survey of relief, drainage, soils, vegetation, population structure, sex ratio, literacy, transport, settlements. The observer needs theoretical knowledge and a scientific, unbiased attitude.
2. Interview: information from the respondent through dialogue. Precautions: prepare a precise list of items; be clear about the survey's objective; win the respondent's confidence and promise secrecy before sensitive questions; keep a friendly atmosphere; use simple, polite language; avoid questions that hurt self-respect or religious feelings; ask at the end for any extra information; thank the respondent.
3. Questionnaire and schedule: written questions with possible answers to tick, or space for opinions; objectives clearly stated. Good for large areas and can be mailed.

• Questionnaire: filled by the respondent, so only literate people can answer.
• Schedule: filled by a trained enumerator who asks the questions, so both literate and illiterate respondents can be covered.

4. Other methods: soil kits and water quality kits measure properties in the field; transducers measure crop and vegetation health.

Secondary sources of data

NCERT section Secondary Source of Data

Secondary data come from published or unpublished records already prepared by others.

Published sources:
1. Government publications: reports of ministries and departments of the Government of India and states, District Bulletins; e.g. the Census of India (Office of the Registrar General), National Sample Survey reports, India Meteorological Department weather reports, state Statistical Abstracts, reports of Commissions.
2. Semi or quasi-government publications: Urban Development Authorities, Municipal Corporations, Zila Parishads.
3. International publications: yearbooks and reports of UN agencies such as UNESCO, UNDP, WHO, FAO; e.g. the Demographic Year Book, Statistical Year Book and Human Development Report.
4. Private publications: yearbooks, surveys and research reports by newspapers and private organisations.
5. Newspapers and magazines: easily accessible.
6. Electronic media, especially the internet, now a major source.

Unpublished sources:
1. Government documents: e.g. village revenue records kept by the patwari.
2. Quasi-government records: periodic reports and development plans of Municipal Corporations, District Councils and Civil Services departments.
3. Private documents: records of companies, trade unions, political and non-political organisations and residents' welfare associations.

Tabulation: absolute data, percentages and index numbers

NCERT section Tabulation and Classification of Data; Data Compilation and Presentation

Raw data are a jumble with little meaning until they are tabulated and classified. A statistical table arranges data in rows and columns: it simplifies presentation, eases comparison, helps readers find information quickly and fits a mass of data into little space.

Data can be presented in three forms:

• Absolute data: original integers, e.g. the total population of India in 2011 (1,21,05,69,573 persons, of which 62,31,21,843 males and 58,74,47,730 females, Census 2011).
• Percentage or ratio: computed from a common base, e.g. literacy rate = (total literates / total population) x 100. Table 1.2 shows India's literacy rising from 18.33 per cent (1951) to 73.0 per cent (2011); male 80.9, female 64.6 in 2011.
• Index number: a measure of change in a variable (or group of variables) over time, place or another characteristic; widely used for price and quantity changes. Simple aggregate method: Index = (sum of current-year values / sum of base-year values) x 100, with the base year = 100.

Worked illustration (Table 1.3, iron ore production, base 1970-71 = 32.5 million tonnes):

Year	Production (mt)	Index
1970-71	32.5	100
1980-81	42.2	42.2/32.5 x 100 = 130
1990-91	53.7	165
2000-01	67.4	207

So production roughly doubled (index 207) in thirty years.

Grouping raw data and frequency distribution

NCERT section Processing of Data; Grouping of Data; Process of Classification; Frequency Distribution

Steps (NCERT example: scores of 60 students, ranging 02 to 96):
1. Decide the number of classes and the class interval from the range of the data: here 10 classes of 10 units (0-10, 10-20 ... 90-100).
2. Classify each value with tally marks using the Four and Cross method: four vertical strokes, and the fifth crosses them.
3. Count the tallies to get the frequency (f) of each class. The table of classes and frequencies is a frequency distribution.

Simple frequency (f): number of observations in a class; their sum is N (here N = 60).

Cumulative frequency (Cf): add each simple frequency to the running total: 4, 9, 14, 21, 27, 37, 45, 51, 56, 60 (last Cf = N). It shows at a glance, for example, that 27 students scored below 50 and 45 below 70.

Forming classes:

• Exclusive method: the upper limit of one class equals the lower limit of the next (20-30, 30-40). A value of 30 goes into 30-40, i.e. each class excludes its upper limit ('20 and under 30').
• Inclusive method: both limits belong to the class (e.g. 50-59 includes 50 to 59); the upper limit of one class is usually 1 less than the lower limit of the next. Each class still spans 10 values.

Frequency polygon and ogives

NCERT section Frequency Polygon; Ogive

• Frequency polygon: a graph of a frequency distribution; useful for comparing two or more distributions on one graph.
• Ogive (pronounced 'ojive'): the curve obtained by plotting cumulative frequencies.
• Less than ogive: use the upper limits of classes and keep adding frequencies (less than 10: 4; less than 20: 9 ... less than 100: 60). It gives a rising curve.
• More than ogive: use the lower limits and start from the total, subtracting each class's frequency (the series runs 60, 56, 51 and so on down to 4 for the last class). It gives a falling curve.
• Both can be drawn on the same graph for comparison.

Data – Its Source and Compilation in real life

Each concept, met in an everyday situation. Read the situation, answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.

Data – Its Source and Compilation: key facts

Literacy rate

(Total literates / Total population) x 100

A percentage computed from a common base.

Index number (simple aggregate)

(Sum of q1 / Sum of q0) x 100

q1 = current year values, q0 = base year values; base year = 100.

Total frequency

$Sumoff=N$

Last cumulative frequency also equals N.

Cumulative frequency

$Cfofaclass=Cfofpreviousclass+fofthisclass$

Used for the less than ogive.

More than series

Start at N; subtract each class frequency in turn

Gives a falling ogive.

Exclusive vs inclusive

Exclusive: 20-30, 30-40 (upper limit excluded); Inclusive: 20-29, 30-39 (both limits included)

Each class spans 10 values in both.

Tricks to remember Data – Its Source and Compilation

Short memory aids. Say each one aloud once, then use it on a question the same day.

• Primary methods

  "O-I-Q-K": Observation, Interview, Questionnaire/schedule, Kits (soil, water, transducers).

  Use it when: Listing primary sources.

• UN data agencies

  "U-U-W-F": UNESCO, UNDP, WHO, FAO.

  Use it when: International publications.

• Ogive direction

  "Less than climbs, more than falls."

  Use it when: Shape of ogives.

• Exclusive method

  "Exclusive kicks out the top": a value at the upper limit moves to the next class.

  Use it when: Placing boundary values.

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

1. 1.What is a datum?Show answer

   A single measurement from the real world.

2. 2.Who fills in a schedule?Show answer

   A trained enumerator, by asking the respondent.

3. 3.Which village-level unpublished record is kept by the patwari?Show answer

   Land revenue records.

4. 4.What is the index of a base year?Show answer

   100.

5. 5.What does the last cumulative frequency equal?Show answer

   N, the total number of observations.

6. 6.What is an ogive?Show answer

   A curve drawn by plotting cumulative frequencies.

Quick revision checklist

The night before the exam: can you do each of these without looking?

• ☐Can you define data and information?
• ☐Can you explain the statistical fallacy?
• ☐Can you list four primary methods of data collection?
• ☐Can you state five precautions for an interview?
• ☐Can you distinguish a questionnaire from a schedule?
• ☐Can you name six published secondary sources?
• ☐Can you calculate an index number by the simple aggregate method?
• ☐Can you make a frequency table using tally marks?
• ☐Can you distinguish exclusive and inclusive classes?
• ☐Can you draw less than and more than ogives?

Data – Its Source and Compilation: frequently asked questions