There are three basic ways of collecting data:
1. Personal interviews:
This method is used when the researcher has access to all the members.
2. Mailing questionnaire:
When the data in a survey are collected by mail, the questionnaire is sent to each individual by mail with a request to complete and return it by given data.
3. Telephone interviews:
In a telephone interview the investigator asks questions over telephone. The advantage of telephone interview are that they are cheaper than personal interview, and can be conducted in a shorter time.
