This unit covers the meaning of statistics, data and data collection, types of data, methods of collecting primary data, problems in primary data collection, secondary data and its sources, merits and demerits of secondary data, and precautions in using secondary data.
Meaning of Statistics
Plural definition
In the plural sense, statistics is defined as facts or information expressed numerically.
An aggregate of facts, numerically expressed, affected by many factors, collected in a systematic manner with a definite purpose, and with a reasonable degree of accuracy are characteristics of statistics in the plural sense.
According to Prof. Horace Secrist, "Statistics may be defined as the aggregate of facts affected to a marked extent by multiplicity of causes, numerically expressed, enumerated or estimated according to a reasonable standard of accuracy, collected in a systematic manner for a predetermined purpose and placed in relation to each other."
Singular definition
In the singular sense, statistics refers to the science of studying statistical methods.
According to Croxton and Cowden, "Statistics may be defined as the science of collection, presentation, analysis and interpretation of numerical data."
Data and Data Collection
Data can be defined as numerical facts or figures or information which are used for the purpose of statistical analysis.
Data are the raw materials for the final statistical conclusions.
Collection of data is the first step in statistical investigation.
Investigator: a person who conducts statistical enquiry and collects the data.
Respondents / informant: persons from whom information are collected.
Statistical units: the items on which measurements are taken.
Data collection is the process of collecting the necessary information from the units of investigation.
Types of Data
- Primary data
- Secondary data
Primary Data
The data collected for the first time by the investigator or researcher and used by them in the statistical analysis are called the primary data.
Methods of collecting primary data
The methods commonly used for the collection of primary data are as follows:
- Direct personal interview
- Indirect oral interview
- Information through correspondence
- Mailed questionnaire method
- Schedules to be filled by enumerators
Direct personal interview: In this method investigators or researchers personally ask the necessary questions and collect the information (data) from the respondents. The data collected by using this method are more accurate and reliable. It is an expensive and time-consuming method. This method is not applicable when the area of inquiry is large.
Indirect oral interview: When the informants hesitate to give information directly, then information are collected with the help of a third person who is in close contact with respondents. Respondents may hesitate to provide the information directly on sensitive topics like drug addiction habit, smoking and alcoholic habits, income, property, diseases such as AIDS, etc. This method is less expensive and takes less time as compared with direct personal interview. It is applicable for a wider area.
Information through correspondence: In this method the investigator appoints correspondents for different parts of the field of inquiry. They collect information and send it to the investigator / central office. This method is more suitable in the news media. It is applicable for a wider area.
Mailed questionnaire method: A set of questions is called a questionnaire. The questionnaires are sent to the respondents at their address by post. The respondents are requested to answer the questions and return them to the investigator by post within the specified time. Manufacturing companies use this method for the promotion of their goods. This method saves time and money and requires less manpower. But this is not applicable when the respondents are not educated.
Schedules to be filled by enumerators: A schedule consists of a set of questions which are filled up by enumerators. Population census and agricultural census follow this method in the Nepalese context.
Problems in collecting primary data
- Lack of money and time
- Lack of transportation facilities
- High degree of non-response error from illiterate respondents
- Lack of expertise and trained manpower for preparing questionnaires and collecting the primary data
- Chance of getting unreliable data in some situations because of the biases of enumerators
Secondary Data
The data which have already been collected by another person or agency and are used by any other person or agency for their statistical work are called secondary data.
Sources of secondary data
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Merits of secondary data
- It saves time and cost of survey.
- If a trained person collects secondary data, the quality of secondary data is better.
- The scope of enquiry can be increased in terms of area and time to be covered.
Demerits of secondary data
- The definitions of terms and units used in secondary data are not usually known.
- Secondary data obtained from two different sources may not be comparable in terms of definitions, units and time covered.
- Some information is omitted.
- Data may not be in the exact form as required by the researcher.
Precautions in using secondary data
- Reliability of data
- Suitability of data
- Adequacy of data