Mail questionnaires They provide excellent control over interviewer effects. Since no interviewer is present, no interpersonal influences are possible. Email questionnaires They suffer from the same problems. Telephone interviews Thy enable sample control and fast data collection. Many marketing contexts, such as political campaigns, need almost overnight information on the effectiveness of the latest promotions.
Telephones reach diverse geographic markets, and can be linked to computers for easy data analysis.
Problems with respondent cooperation may become increasingly important over time. They haven't quite integrated telephony yet. Until we gain an audio voice to supplement our written voice, online interviewing can't replace telephone interviewing. When it does, this form of data collection will retain all of its advantages without accruing any disadvantages. A combined audio and video connection will merge this form of data collection with the personal interview.