A statistical survey is a scientific process of collection and analysis of numeric data. Human population survey is used in government, health, social science, and marketing sectors. The need for new data starts when data do not yet exist or when existing data do not fully satisfy the needs of the person or organization.

In Statistics, data collection is a process of gathering information from all the relevant sources to find a solution to the research problem. It helps to evaluate the outcome of the problem. The data collection methods allow a person to conclude an answer to the relevant question. Most of the organizations use data collection methods to make assumptions about future probabilities and trends. Once the data is collected, it is necessary to undergo the data organization process.

Data can be classified into two types, namely primary data and secondary data. Data collected for the first time keeping in a view the objective of the survey is called primary data.  Secondary data refers to data that is collected by someone other than the primary user. Common sources of secondary data for social science include censuses, information collected by government departments, organizational records and data that was originally collected for other research purposes.

Collection of Primary Data:

Data collected for the first time keeping in a view the objective of the survey is called primary data. It is collected by personal interview, questionnaire, through telephones and mails. It is collected by census method or sampling method.

Advantages of Primary Data:

• It is collected with specific goals and purpose which cuts out the possibility of wasting of resources.
• It is reliable because the researcher can replicate the procedure to check the results, due to the knowledge of procedures of data collection and analyzation.
• It is up-to-date- data since it is collected fresh.
• This data is collected from the population in question, hence can be considered as authentic and thus bias of third parties can be avoided.
• The course of the survey can be changed anytime as per the new requirement of the survey.

Disadvantages of Primary Data:

• It is the costliest method of data collection.
• It is a time-consuming method.
• This method requires a large sample space for the credibility of the data obtained.

Observation Method:

In this method, is obtained by direct observation by the investigator without asking from the respondent. This method is free from the willingness of the respondent and hence the possibility of bias on the part of the respondent is avoided.

The accuracy of data by this method depends on the ability, training, and attitude of the investigator. This method is suitable when the scope of the investigation is narrow. The investigation is confidential. requires personal attention on part of the investigator and requires accuracy.

Merits of Observation Methods:

• We get original and actual data.
• Satisfactory data can be obtained through indirect questioning.
• Data is homogeneous and comparable.
• Additional information beyond the scope of the survey can be obtained.

Demerits of Observation Method:

• It is an expensive and time-consuming method.
• This method is not applicable when the scope of the investigation is wide.
• The information provided by this method is very limited.
• Some of the busy people may not be accessible to direct observation.
• Most of the data collected by this method are confidential.

Interview Method:

Primary data may be collected either through personal interviews or through telephonic interviews.

Direct Oral Interview Method:

In the direct oral interviews or personal interviews, the interviewer asks questions gen­erally in a face to face contact.

This method is effective when there is a rapport between the interviewer and the respondent. Proper training is required for such an investigation. The interviewer should have a friendly, conventional and unbiased approach towards the respondent.

Merits of Direct Oral Method:

• By this method in depth, more reliable and personal information may be obtained easily.
• Some unexpected and useful information can be obtained.

Demerits of Direct Oral Method:

• It is a very expensive and time-consuming method,
• Some busy people may not be easily accessible.
• The respondent may give wrong, biased and imaginary information
• Proper training is required for carrying out the oral direct interview.
• There is a possible bias on part of both the interviewer and the respondent.
• The possibility of imaginary information on part of respondent exists.

Direct Telephonic Interview Method:

In telephonic interviews, contact is made with the respondents through a telephone. In this method, a properly trained staff with command over language is required.

Merits of Telephonic Interview Method:

• It is flexible and faster method than other methods.
• Less staff is required. No field staff is required.
• It is cheaper and less time-consuming.
• A wider representation of the sample is possible.
• The recall is easy and there is a higher rate of response.
• The conversation can be recorded without embarrassing the respondents.
• Suitable time for respondent can be fixed.

Demerits of Telephonic Interview Method:

• The sur­veys are restricted to respondents who have telephonic facilities
• Sometimes the respondents are given less time to give answers.
• Questions should be short, unambiguous and to the point.
• It is not suitable for intensive surveys where detailed answers are re­quired.
• Less information is collected.

Indirect Oral Interview:

This method is used when the area to be covered is large. The investigator collects information from the third parties and eyewitnesses or the head of the organization. This method is used by the police department to investigate the theft, murder, fire, etc. In this method, probable information providers are located and questions are asked to them. Inquiry committees by government use this method to find the facts. This method is used when direct sources of information are not available.

Merits of Indirect Oral Interview:

• It is time and resource-saving, cost-efficient method.
• Confidential information can be collected
• Some unexpected and useful information can be obtained.
• Information is likely to be reliable and unbiased.

Demerits of Indirect Oral Interview:

• The degree of accuracy of the information is less.

Questionnaire Method:

In this method, a well drafted and easy to understand questionnaire is mailed to the person concerned with a request (covering letter) to answer the questions and return the questionnaire. The covering letter also conveys the purpose of the survey it gives assurance of keeping the shred information confidential.

Merits of Questionnaire Method:

• There is a low cost per respondent even when the population is large and is wide­spread geographically.
• More questions may be asked because the respondent is taking his own time to complete the questionnaire.
• It is free from the bias of interviewer as answers are the respondent’s own words. Thus interviewer does not influence the respondent.
• A large number of resp[onses can be obtained in a short span of time.
• Respondents, who are not easily approachable, can also be reached conveniently.
• Respondents are given enough time to give well-thought answers.

Demerits of Questionnaire Method:

• Low response rate.
• It can be used only with educated and cooperative respondents.
• The questionnaire may be partially filled.
• The misunderstanding may not be clarified.
• The respondents cannot be encouraged to think well before answering.
• The control of the questionnaire may be lost once it is sent.
• The method is the slowest of all methods.
• It is difficult to know whether the questionnaire is filled by the desired respondent.

Design of the Questionnaire:

Initial Consideration:

• Type of information required: To design a good questionnaire start with the end in mind and be clear what we are trying to find out and how we will use the data.
• Type of respondents: The local language, culture, beliefs, traditions play very important roles in designing a good questionnaire.
• Type or method of Survey: If mailed questionnaire method is used, then the questions should be short, self-explanatory, and unambiguous. The questions which are not clear should be explained or provided with proper options.

Question content:

• The relevance of a question: Keep the questionnaire concise and focussed on the objectives of the survey. Avoid asking too many questions about too many topics.
• Clarity of question: Make it easy for people to answer the questions. The questions should be short, self-explanatory, and unambiguous. Avoid leading and multiple questions.
• Ability and Willingness to Answer: Phrase the question simply and unambiguously.

Steps to be Followed in Questionnaire Construction ind Writing the Report:

1. Determining the scope of the questionnaire.
2. Deciding the type of questions (close ended or open ended) to be asked.
3. Preparing the draft questionnaire.
4. Pretesting the questionnaire with a sample population.
5. Revising the questionnaire according to the suggestions received.
6. Distributing of the questionnaire to the actual sample.
7. Sending reminders to the population under study.
8. Receiving the responses.
9. Analysing and interpreting of the data received.
10. Writing the report.

Schedule Method:

This method of data collection is very much like the collection of data through questionnaires, with little difference that lies in the fact that schedules (proforma containing a set of questions) are being filled in by the enumerators who are specially appointed for this pur­pose. Enumerators explain the aims and objects of the investigation and also remove the difficulties which any respondent may feel in understanding the implications of a particular question.

This method is very useful in extensive inquiries and can lead to fairly reliable results. It is, however, very expensive and is usually adopted in investigations conducted by governmental agencies or by some organizations. Population census all over the world is con­ducted through this method.

Selection of Method to Collect Primary Data:

For the selection of an appropriate method, the objective, nature and scope of study, the availability of time and funds, and the level of precision required are to be taken into consideration

Secondary Data Collection:

Secondary data collection is the process of gathering data that has already been collected and published by others for a different purpose. This data is collected from existing sources, such as published reports, databases, official statistics, or other publicly available data sources. Examples of secondary data sources include academic journals, government reports, industry reports, and publicly available datasets. An advantage of secondary data collection is its cost-effectiveness, as the data is already available and does not require additional resources for data collection.

However, there are also limitations to secondary data collection. The data may not always be tailored to the specific research question, or may lack the desired level of detail. There may also be concerns about the quality, reliability, or accuracy of the data, as it is collected by others and may not have undergone the same level of scrutiny as primary data.

Conclusion:

Data collection methods play an important role in obtaining well-rounded and informed results that can greatly influence business decisions. By using appropriate methods of collection of data , researchers can gather relevant, reliable and high-quality data that provides insights and supports evidence-based decision-making. Sometimes, this means choosing a single appropriate data collection method, while other times it may require a mix of different methods. These methods can be either qualitative or quantitative, or they could be primary or secondary, depending on the complexity, volume and kind of data required for the research.