Data Collection: Collection of data constitutes the first step in a statistical investigation. Utmost care must be exercised in collecting data as because they form the foundation of statistical method. If data are faulty, the conclusion drawn can never be reliable.
1. Types of Data: Generally data are of two types-
a) Primary Data: The data which are originally collected by an agency for the first time for any statistical investigation are said to be primary data.
b) Secondary Data: The data which have already been collected by some agency and taken over from there and used by any other agency for their statistical work are termed as secondary data. So in simple if a primary data collected for a statistical investigation are used in other statistical investigation then those data are called as secondary data.
2. Tools and Techniques of Data or Information Collection: The primary data or information can be collected by the following means-
a) Observing Behaviors of Participants: This method specifies the conditions and methods at making observation. In this method, the information is sought by way of investigator’s own direct observation without asking from the respondent. The main advantage of this method is that subjective bias is eliminated, if observations are done accurately. It is the most commonly used method especially in studies relating to behavioral science.
b) Questionnaire Method: Under this method, a list of questions pertaining to the survey (known as questionnaire) is prepared and sent to the various informants by post. The questionnaire contains questions and provides space for answer. A request is made to the informants through a covering letter to fill up the questionnaire and sent it back within a specified time. The respondents have to answer the questions on their own. The questionnaire can be delivered directly hand by hand, through surface post or as an electronic questionnaire.
In preparing a research questionnaire general question, question wording to collect personal information, use of unfamiliar terms and jargon, etc. should be avoided. Further, before distribution of a research questionnaire at least two pre-tests should be conducted and it is very much needed.
c) Interview Method: This involves listening to or integrating informants. The interview method of collecting data involves presentation of oral-verbal stimuli and reply in terms of oral – verbal responses. So, under this method of collecting data, there is a face to face contact with the persons from whom the information is to be collected. The interviewer asks them question pertaining to the survey and collects the desired information. This method can be used through personal interview, telephone interview, Chat, Audio Conferencing, Video Conferencing, etc. The interview can be structured, semi structured or open interview.
d) Schedules Method: In this method of data collection, the ennumerator or interviewers who are specially appointed for the purpose along with schedules, go to the respondents, put to them the questions from the Performa in the order the questionnaire are listed and record the replies in the space meant for the same in the Performa. In certain situation, schedules may be handed over to respondents and ennumerators may help them in recording their answer to various questions in the said schedules. Ennumerator explains the aims and objectives of the investigation and also removes the difficulties which respondents may feel in relation to understanding the implication of a particular question or a definition or concept of difficult term. This method has the advantage over the questionnaire method in the sense that the respondents have no scope to misunderstand any question and thereby putting irrelevant answer.
e) Information from Correspondents: Under this method, the investigator appoints local agent or correspondents in different places to collect information. These correspondents collect and transmit information to the central office where the data are processed. The special advantage of this method is that it is cheap and appropriate for extensive investigation. However, it may not always ensure accurate results because of the personal prejudice and bias of the correspondents. Newspaper agencies generally adopt this method.
Besides the above methods, nowadays many big companies also follow some other method for primary data collection like warranty card, Distributor or Store Audit, Consumer Panels, Projective Techniques, Depth Interview, Content analysis, etc.
In most of the studies the investigator finds it impracticable to collect first hand information on all related issues and as such he/she makes use of the data collected by others. The secondary data can be collected by way of examining historical and other records, literature and proverbs. If data available in secondary sources are reliable, suitable and adequate then only the secondary data should be collected.