Planning for Collection of Statistical Data

Planning for the collection of statistical data is a crucial step in any statistical investigation. It involves systematic preparation to ensure that the data collected is relevant, accurate, and sufficient for analysis.

• Objective and Scope of Statistical Investigation: Clearly defining the purpose and boundaries of the study.
• Sources of Information: Identifying where the data will be obtained from.
• Time and Type of Statistical Enquiry: Deciding when and how the data will be collected.
• Determination of Statistical Tools: Selecting appropriate methods and instruments for data collection and analysis.
• Degree of Accuracy: Establishing the level of precision required in the data.

This planning ensures that the data collection process is efficient and effective, minimizing errors and biases.

Sources of Data

Data can be sourced from two main categories:

• Internal Sources: Data collected from within the organization or study area.
• External Sources: Data obtained from outside the organization, which can be further divided into:
• Primary Data: Original data collected firsthand for the specific purpose of the study.
• Secondary Data: Data previously collected for other purposes but used for the current study.

Difference Between Primary and Secondary Data:

Basis	Primary Data	Secondary Data
Meaning	Data collected firsthand for a specific study.	Data collected earlier for other purposes.
Source	Direct from respondents or observations.	From published or unpublished records.
Originality	Original and authentic.	Not original; may be modified.
Cost	Generally high due to collection efforts.	Relatively low or no cost.
Availability	May be time-consuming to collect.	Readily available.
Adjustment	Can be tailored to study needs.	Limited scope for adjustment.

Methods of Collection of Primary Data

Primary data collection methods include:

• Direct Personal Observation: Observing the subject or phenomenon directly.
• Indirect Oral Investigation: Collecting data through verbal communication.
• Telephone Interview: Gathering information via phone calls.
• Information through Local Sources & Correspondents: Using local contacts to obtain data.
• Mailed Questionnaires: Sending questionnaires by mail for respondents to fill.
• Questionnaires Filled by Enumerators: Trained personnel collect data by filling questionnaires during field visits.

Selection of Appropriate Method

The choice of data collection method depends on:

• The Nature of Investigation: Type and complexity of data required.
• Object and Scope of Enquiry: Purpose and extent of the study.
• Financial Resources: Budget available for data collection.
• Degree of Accuracy Desired: Precision needed in data.
• Time Factor: Time available for data collection.

Qualities of a Good Questionnaire

• Brief and to the point.
• Simple, clear, and unambiguous questions.
• Appropriate nature of questions (open or closed).
• Use of proper and understandable words.
• Questions should be answerable by the informant.
• Questions capable of objective answers.
• Should not hurt sentiments or communities.
• Avoid personal or sensitive questions.
• Proper sequence of questions.
• Clear instructions for filling the questionnaire.
• Well-set format and layout.
• Tested for accuracy through pilot surveys.

Collection of Secondary Data

Secondary data can be:

• Published: Data available in official publications, reports, and documents.
• Unpublished: Data found in diaries, letters, unpublished biographies, etc.

Published Sources of Data

• Publications of international bodies.
• Government publications.
• Reports of committees and commissions.
• Publications and reports of trade associations and chambers of commerce.
• Semi-government publications.
• Private publications.

Unpublished Sources of Data

Includes diaries, letters, and unpublished biographies which may provide valuable information not available elsewhere.

Reliability of Secondary Data

When using secondary data, it is important to assess:

• Whether the data are reliable and authentic.
• Whether the data are suitable for the intended purpose.
• Whether the data are adequate and sufficient.

Important Sources of Secondary Data in India

• Census of India: Provides comprehensive demographic data. The first census after independence was conducted in 1951.
• National Sample Survey Organisation (NSSO): Conducts nationwide surveys on socio-economic issues.

Techniques of Data Collection: Census and Sample Investigation

There are two main techniques for data collection:

• Census Method: Collecting data from every unit of the population or universe.
• Sample Survey: Collecting data from a representative subset of the population to infer about the whole.

Census Survey

Census survey involves complete enumeration of all units in the universe related to the study.

• Advantages:
• More accurate and reliable data.
• Allows intensive study.
• Suitable for diverse information.
• Demerits:
• Costly and time-consuming.
• Requires more labor.
• Not feasible in some situations.

Merits and Demerits of Sample Investigation

• Merits:
• Reduced cost.
• Faster data collection.
• Greater scope and flexibility.
• Can provide detailed enquiry.
• Administrative convenience.
• Often the only feasible method.
• Demerits:
• Possibility of misleading conclusions.
• Difficulty in selecting a truly representative sample.
• Requires specialized knowledge.
• Challenges in restricting study to sample only.
• Difficulty in framing an appropriate sample.

Essentials of Sampling

• Representativeness: Sample should reflect the population.
• Independence: Selection of one unit should not influence another.
• Homogeneity: Units should be similar in characteristics.
• Adequacy: Sample size should be sufficient.
• Similar Regulating Conditions: Conditions should be uniform across units.

Methods of Sampling

• Random Sampling Method
• Purposive or Deliberate Sampling Method
• Mixed or Stratified Random Sampling Method
• Systematic Random Sampling Method
• Extensive Sampling Method
• Multi-stage Sampling Method / Cluster Sampling
• Quota Sampling Method
• Convenience Sampling Method