A telephone survey is a type of opinion poll used by researchers. As with other methods of polling, their are advantages and disadvantages to utilizing telephone surveys.
Advantages
- Large scale accessibility. About 95% of people in the United States have a telephone (see ), so conducting a poll by via telephone is a good way to reach most parts of the population.
- Efficient data collection. Conducting calls via telephone produces a quick process, allowing researches to gain a large amount of data in a short amount of time. Previously, pollsters physically had to go to each interviewee's home (which, obviously, was more time consuming).
- Inexpensive. Phone interviews are not costly (e.g., telephone researchers do not pay for travel).
- Anonymity. In certain polls, the interviewer or interviewee (or both) may wish to remain anonymous, which can be achieved if the poll is conducted over the phone by a third party.
Disadvantages
- Lack of visual materials. Depending on what the researchers are asking, sometimes it may be helpful for the respondent to see a product in person, which of course, cannot be done over the phone.
- Call screening. As some people do not answer calls from strangers, or may refuse to answer the poll, poll samples are not always representative samples from a population due to what is known as non-response bias. In this type of bias, the characteristics of those who agree to be interviewed may be markedly different from those who decline. That is, the actual sample is a biased version of the population the pollster wants to analyze. If those who refuse to answer, or are never reached, have the same characteristics as those who do answer, then the final results should be unbiased. However, if those who do not answer have different opinions, then the results have bias. In terms of election polls, studies suggest that bias effects are small, but each polling firm has its own techniques for adjusting weights to minimize selection bias.
- Undercoverage. Undercoverage is a highly prevalent source of bias. If the pollsters only choose telephone numbers from a telephone directory, they miss those who have unlisted landlines or only have cell phones (which is is becoming more the norm). In addition, if the pollsters only conduct calls between 9:00 a.m and 5:00 p.m, Monday through Friday, they are likely to miss a huge portion of the working population—those who may have very different opinions than the non-working population.