What are the merits & Demerits of Direct personal observation and Indirect Oral Interview?

In the direct personal observation method, the investigator collects data by having direct contact with units of investigation.The accuracy of data depends upon the ability, training and attitude of the investigator. 

The direct personal observation method is suitable where - 

- The scope of investigation is narrow 

- Investigation is confidential and requires personal attention of the investigator 

- Accuracy of data is important 

Merits and demerits of direct personal observation 

- Merits: 

1) We get original data. 

2) we get more accurate and reliable data. 

3) Satisfactory information can be extracted by the investigator through indirect questions. 

4) Data are homogeneous and comparable. 

5) Additional information can be gathered. 

6) Misinterpretation of questions can be avoided.

 Demerits: 

1) It is time consuming and costs more. Indirect oral interview is used when area to be covered is large. The data is collected from a third party or witness or head of institution. This method is generally used by police department.

Merits and demerits of indirect oral interview - 

Merits: 

1) It is economical in terms of time, cost and manpower. 

2) Confidential information can be collected. 

3) Information is likely to be unbiased and reliable. 

Demerits: 

 1) The degree of accuracy of information is less.