Math 3 Honors: Sampling Bias

Voluntary Response

People choose to respond. Usually only people with very strong opinions respond. An example would be the surveys in magazines that ask readers to mail in the survey. Other examples are call-in shows, American Idol, etc. The way to determine voluntary response is: Self-Selection!

Convenience

Sampling people who are easy to ask, can produce biased results. An example would be stopping friendly-looking people in the mall to survey. Another example is the surveys left on tables at restaurants- a convenient method! The data obtained by a convenience sample will be biased - however this method is often used for surveys and results reported in newspapers and magazines

Undercoverage

Some groups of population are left out of the sampling process. Suppose you take a sample by randomly selecting names from the phone book - some groups will not have the opportunity of being selected! (people with unlisted numbers, people without phone numbers, people with ONLY cell phones)

Non-Response

Occurs when an individual chosen for the sample can’t be contacted or refuses to cooperate. People are chosen by the researchers, BUT refuse to participate, NOT the same as voluntary response! Because of huge telemarketing efforts in the past few years, have a MAJOR problem with nonresponse

Response

Occurs when the behavior of respondent or interviewer causes bias in the sample. Suppose we wanted to survey high school students on drug abuse and we used a uniformed police officer to interview each student in our sample - would we get honest answers?

Lurking Variables

are variables that cause results in a study but may not have been taken into consideration by the experiments or surveyors

Confusing Wording

Wording can influence the answers that are given. Questions must be worded as neutral as possible to avoid influencing the response.