Direct Personal Investigation

This method is also known as the interview method. It is the method, by which data are personally collected by the investigator from the informants. In other words, there is face to face contact with the person from whom the information is to be obtained.

He has to be on the spot to conduct the inquiry and has to meet the people who a possession of the required data. Thus, if a person wishes to collect data about the wages of the workers of Bombay Cloth Mills, he would have to go to the Mill to contact workers and obtain the desired information.

Suppose we have to conduct a statistical enquiry:

Consumption of Pears soap by the citizens of Ambala City.


For this we shall approach the randomly selected citizens of Ambala City and shall collect the necessary data.

Here it is of immense use to quote that investigator must be trained, tad intelligent so that data collection must be successful.


The method of collecting primary data is suitable particularly in following cases:

(i) Detailed and supplementary information can be collected.


(ii) Where data are to be kept secret.

(iii) Where the area of investigation is limited.

(iv) Where there is need for personal interview.

(v) Where importance is given to originality.


(vi) Where importance is given to purity.



The data collected so are original in character.



Information collected by the investigator is reliable and is beyond doubt.

(iii) Economical:

This method of collecting data is economical in case the field investigation is limited.

(iv) Elastic:


This method is fairly elastic as the investigator can make certain changes in the questionnaire according to the need of the situation.


This method ensures greater accuracy.

(vi) Other Information:


Investigator can collect the supplementary information about the informant’s personal characteristics.


(i)Not Suitable for Wide Areas:

This method cannot be completed with reasonable time if the field of investigation is wide.

(ii)More Expensive:

This method is more expensive where the number of pen to be interviewed is large.

(iii)Personal Prejudice:

This method of investigation is highly prone to personal prejudice of the investigator.

(iv) Trained Personal:

The interviewers must be thoroughly trained and unbiased otherwise they may not be able to collect the information.


(i) Questions should be straight and simple.

(ii) Investigator should be polite.

(iii) Investigator should keep himself away from personal prejudices.

(iv) Investigator should not be biased.

(v) Investigator should be familiar with the cultural, tradition and the language of the concerned area.

Indirect Personal Investigation

In this method, the investigator approaches the persons directly or indirectly concerned with the subject matter of the inquiry to obtain the necessary information. Under this method, a small list of questions relating to the investigation is prepared and these questions are asked from different persons and their answers are recorded.

The persons to whom these questions are put are known as witnesses. Generally, this method of investigation is employed where the required information is of complex nature and the informants are not inclined to respond if approached directly.

For example, we want to know the number of students of a college who take drugs. For this purpose, primary data by personal investigation cannot be successful because the students may not provide correct information as regards their drug habits.


(i) Where the concerned informants are unable to give information due to their ignorance.

(ii) Where the field of investigation is large.

(iii) Where the problem of investigation is complex.

(iv) Where the sources of information are required to be tapped.

(v) Where some secret or sensitive information is to be collected.



Under this method lot of time, labour and money can be saved.

(ii)Wide Area:

This method is applied where the field of investigation is wide.

(iii) Quick Work:

Under this method, work is done very quickly.


In this method, the investigator can very easily collect the information.

(v) Free from Bias:

This method is relatively free from personal prejudice.


It is relatively a simple approach of the collection of data.

(vii)Expert Opinion:

Under this method, an investigator can seek opinion of the experts.


(i)Lack of Uniformity:

Data collected by this method lacks uniformity.

(ii)Lack of Accuracy:

The data collected by this method lacks accuracy because information is obtained from the persons not concerned with the subject matter of the inquiry.

(iii) Biased:

There is every possibility of personal prejudice of the witnesses giving information.

(iv) Doubtful Conclusions:

This method may lead to doubtful conclusions.


(a) It is necessary that the investigator should have full faith in the respondents,

(b) The number of witnesses should be sufficiently large.

(c) Efforts should be made to make cross check system to ascertain the accuracy.

(d) Only those respondents should be selected who possess sufficient knowledge about the proposed investigation.

(e) It must be ensured that interviewers are not subjective in their approach.

Information from Correspondents

In this method, data is collected from different places from local persons known as correspondents. The investigator appoints local agents and correspondents in different parts of the field of inquiry. These correspondents collect the data from time to time and transmit the same to the central office where these are processed.

Basically, this method is employed by the Govt, departments in those cases where regular information is to be obtained from far-off places. For instance, estimates of agricultural crops are made by the school teachers and are furnished to the Govt. Similarly, this method is employed by the newspapers which require information in various fields regularly.


(a) When the regular and continuous information is required.

(b) When the accuracy of the data is modestly required.

(c) When the field of investigation is relatively wide.


(i) Wide Sphere:

This method is applied where the field of investigation is very vast.


Under this method, time, money and labour can be well saved,


The appointed correspondents keep on supplying regular’ information.

(iv) Suitable for Special Purpose:

This method is suitable for some sped purpose of investigations.


(i) Lack of Originality:

This method lacks originality.

(ii) Lack of Accuracy:

This method cannot be used where high degree of accuracy is required.

(iii)Lack of Uniformity:

Correspondents being large, they give different reports

(iv)Time Consuming:

A lot of time is consumed to collect the information.

(v)Personal Prejudice:

This method suffers from the personal prejudice of the correspondents.


(a) Proper precautions should be made in the appointment of correspondents.

(b) Number of respondents should be fairly large and reasonable.

(c) It must be kept in mind that the correspondents are educated and familiar with the problem.

(d) Efforts should be made to minimize the personal bias statements/views of the correspondents.

Mailed Questionnaire Method

According to this method, the investigator prepares a list of questions pertaining to the field to investigation and sent to various informants. The respondents send back the questionnaire duly filled within the prescribed period.


(a) The field of investigation is very large.

(b) The respondents are literate to respond to the request of the investigator.


(i) Originality:

The data so collected are very much original.

(ii) Wide Sphere:

This method is applied where the field of investigation is wide.

(iii) Economy:

This method is very economical as it involves the cost of printing the schedules and sending them to the informants.

(iv) Less Chance of Error:

There exists less chance of error.


(i)Lack of Interest:

This method lacks interest on the part of respondents.

(ii) Effect of Partiality:

Under this method, personal bias may affect the correctness of the data.

(iii) Fear of Informants:

Many informants may not return the completed questionnaire due to fear.


(a) Questionnaire should be simple, short and attractive.

(b) Language of the questionnaire should be effective.

(c) Object of the investigation must be clearly stated.

(d) Questionnaire should be accompanied by a self-addressed and stamped envelope for early action.

(e) Questionnaire should not hurt the informants.

(f) No personal question or biased questions be asked.

Information through Questionnaire with the help of Enumerator

In this method, information is collected by interviewing the persons who are likely to be in passion of the required information.

The enumerator, personally visits informants along with this schedule, asks questions and note down their replies in his own language. Usually, this method is used by the govt, and semi. Govt, organizations, big business houses, research institutes etc.


(i) Wide Scope:

This method can cover large area of investigation.

(ii) Accuracy:

Since information is collected by the trained and experienced personals, it is relatively accurate.

(iii) Free from Bias:

It is free from personal bias.

(iv)Less time consuming:

This method consumes less time.

(v)Personal Relations:

Since, the information is collected by the enumerator himself there is no lack of response.


(i)Expensive Method:

This method is quite costly as the enumerators are paid persons. Thus, it is not economical.

(ii) Trained Personal:

Data collected may not be reliable if it is collected un experienced persons.

(iii)Time Consuming:

This method is more time consuming as compared to methods.


The enumerator may be biased person resulting in partial answers to the investigation.

(v)Inability of Enumerator:

Data collected may not be accurate simply dm inefficiency of enumerator.


(a) Enumerator should be a man of high character and integrity.

(b) Enumerator should be educated and a trained person.

(c) Enumerator must be conversant with the local conditions.

(d) The Enumerator should be polite, tactful, laborious, and honest to his assigned work.