Under this method, the investigator makes a questionnaire pertaining to the field of investigations. Blank spaces are left for writing answers. The questionnaire is sent to the respondent along with a covering letter, for soliciting their cooperation. .
Merits—
(i) Wide Coverage—This method is used for extensive enquiries covering very wide area.
(ii) Economy—This method is economical as it requires less time money and labour.
Demerits—
(i) Limited Scope—This method is applicable only where respondents are educated.
(ii) Less Accuracy and Precision—Under this method, the accuracy of data cannot be testified.