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To find the percentage of households in a town who own more than one motor vehicle, a survey will ask the next 100 drivers at a popular gas station if there is more than one motor vehicle in their household. Is this survey biased and if so, what is the main type of bias?
Because the survey is being conducted on drivers at a gas station, people/households who do not own a motor vehicle will not be included in the survey.
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The best way to reduce variability in an unbiased sample is to __________.
Using random sampling methods alone does not reduce variability in a sample; they only reduce bias. The best way to reduce variability in an unbiased sample is to take a bigger sample—the bigger the population of the sample, the less widespread the results will be. It is important to remember that if there is bias present in a sample, a large sample population size (n value) will not be enough to overcome the bias.
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Identify the type of bias:
A radio station polls listeners on a controversial issue by talking to people who call in to the station.
Voluntary response bias usually results when those sampled are volunteers who select themselves.
Voluntary response bias can cause results to over represent those who have a strong opinion.
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Identify the type of bias:
A researcher wants to know what proportion of people in the United States favor student debt reform. The researcher goes to five universities and at each asks people whether they favor student debt reform.
This is an example of undercoverage because the researcher did not speak to people who were not affiliated with a university. Therefore the researcher did not adequately sample all members of the overall population (people in the United States).
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Identify the type of bias:
A researcher wants to know what proportion of coffee drinkers would pay more than $5 for a coffee drink. The researcher asks the following question:
"Do you agree that $5 is way too much to pay for a simple coffee"
By using the words way too much and simple coffee, the researcher is introducing bias into their question by causing people to favor one response over another.
To avoid this sampling bias, the researcher should use more neutral wording, such as "Agree or diasgree- I would pay $5 or more for a coffee drink."
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Identify the type of bias:
A researcher wants to know whether students at a particular university have ever cheated on a test. The researcher walks up to 100 random students and asks them the following question:
"Have you ever cheated on a test or exam?"
Many people are reluctant to be honest about their bad behaviors, especially if they don't believe the survey is confidential. This will cause participants to be more likely to respond with whatever is more socially acceptable.
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You are trying to conduct a survey of students within a college community to see if you should cut funding to the athletics department to save money. Which of the following manners of conducting this survey would lead to the least bias possible?
The correct answer (random sample of 300 students) includes a random sample which will reduce in bias and also is given to be done in person which reduces completion bias. It is also taken from the whole population of students and is a large sample which makes it a good representation of the population. Sending out a questionnaire has completion bias because the only people that will send it back will have strong and possibly biased beliefs already. The hot line has the same effect as those that have strong and biased opinions will be the ones to do it. Pulling students aside as they walk by is not a truly randomly constructed sample and using only 10 students is not a good representation of a whole college. Selecting a sample of just athletes is very biased as they will not want their programs cut.
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