1) Personal interview

An interviewer asking questions generally face-to-face to other persons conductspersonal interview. This sort of interview may be in the form of direct personalinvestigation or it may be an indirect oral investigation. This method is particularlysuitable for intensive investigations.

Advantages

1.More information and that too in greater depth can be obtained.2.Interviewer can overcome any resistance, if any, of the respondents; thisinterview can be made to yield an almost perfect sample of he population.3.There is greater flexibility as questions can be restructured as when needed,especially in the unstructured interviews.4.Observation method can supplement verbal recording of answers.5.Personal information can be obtained easily in this method.6.Sample control can be maintained, as non-response generally remains low.7.Unlike mailed questionnaire, the interviewer can usually control which personswill answer the questions.8.The interviewer can catch the respondent off-guard and thus record thespontaneous reactions.9.The language of the interview can be changed according to the educationlevel of the respondent.10.The interviewer can collect supplementary information about respondent'spersonal characteristics and environment, which helps while interpreting,results.

Disadvantages

1.It can be quite expensive method, especially when large and widespreadgeographical sample is taken.2.Possibility of bias of interviewer and respondent is maximum.3.Certain respondents such as important officials cannot be approachableunder this method.4.It is time-consuming especially when sample is large and re-calls orespondents are to be made.5.Sometimes the presence of he interview can over-stimulate he respondentand he may give imaginary answers to make the interview interesting.6.Under the interview method the organization required for selection, trainingand supervising the field-staff is more complex with formidable problems.7.Interviewing at times may introduce systematic errors.

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8.Interview presupposes a proper rapport with respondents for free and frankresponses, which is not always possible.

2) Telephone interviews

This method of collecting information consists contacting information consistscontacting respondents on telephone itself. It is not a very widely used method, butplays important role in industrial surveys in developed regions.

Advantages

1.It is more flexible in comparison to mail method.2.It is faster in obtaining information than other methods.3.It is cheaper compared to personal interviews; here the cost per response isvery low.4.Recall is easy; callbacks are economic and simple.5.There is higher rate of response than mailing method6.Replies can be recorded without causing embarrassment to respondents.7.Interviewer can explain requirements more easily.8.Access can be gained to respondents who otherwise cannot be contacted for one reason to other.9.No field staff is required.10.Wider distribution of sample is possible.

Disadvantages

1.Little time is given to respondents to answer, as these types of interviews donot last for more than 5 minutes.2.Survey is restricted to people who have telephones.3.Cost plays a major part in extensive geographical coverage.4.It is not suitable for interviews having comprehensive answers to variousquestions.5.Some extent of interviewer's bias exists.6.Questions have to be short and probes are difficult to handle.