http://www.ck12.org Chapter 6. Planning and Conducting an Experiment or Study
a particular marsh area and spends the month of September, during mating season, cataloging sightings of
moose. What two types of sampling are evident in this example?- The local sporting goods store has a promotion where every 1000thcustomer gets a $10 gift card.
For questions 5-9, an amusement park wants to know if its new ride, The Pukeinator, is too scary. Explain the type(s)
of bias most evident in each sampling technique and/or what sampling method is most evident. Be sure to justify
your choice.
- The first 30 riders on a particular day are asked their opinions of the ride.
- The name of a color is selected at random and only riders wearing that particular color are asked their opinion
of the ride. - A flier is passed out inviting interested riders to complete a survey about the ride at 5 pm that evening.
- Every 12thteenager exiting the ride is asked in front of his friends: “You didn’t think that ride was scary, did
you?” - Five riders are selected at random during each hour of the day, from 9 am until closing at 5 pm.
- There are 35 students taking statistics in your school and you want to choose 10 of them for a survey about
their impressions of the course. Use your calculator to select aSRSof 10 students. (Seed your random number
generator with the number 10 before starting). Assuming the students are assigned numbers from 1 to 35,
which students are chosen for the sample?
Review Answers
- (a) All high school soccer players. (b) Each individual high school soccer player. (c) A census. (d) Boys,
students from other areas of the country of different socio-economic or cultural backgrounds, if she is on a
varsity team, perhps JV or freshman soccer players might have different preferences. (e) There are multiple
answers, which is why the explanation is very important. The two most obvious sources are: Convenience
bias, she asked the group that was most easily accessible to her, her own teammates. Incorrect Sampling
frame, boys or some of the other undercovered groups mentioned ind, have no chance of being included in
the sample. (f) The sampling frame. (g) Stratification. - This is incorrect response bias. You are intentionally answering the question incorrectly so as to not antagonize
the giant talking snake! - The biologist is using her knowledge of moose behavior to choose an area and a time in which to estimate the
population, this is judgment sampling. She has also selected one particular lake to estimate the entire region,
which could be considered a form of cluster sampling. - Systematic sampling. The customer is selected based on a fixed interval.
- Convenience bias. The first 30 riders is an easy group to access. Incorrect Sampling Frame. The first riders of
the day are likely to be those who are most excited by high-thrill rides and may not have the same opinions as
those who are less enthusiastic about riding. - Cluster sampling. A group is chosen because of a natural relationship that does not necessarily have any
similarity of response, i.e. we have no reason to believe that people wearing a certain color would respond
similarly, or differently, from anyone else in the population. - Voluntary response bias. Participants will self-select. Non-response bias. A large percentage of potential
participants are not going to want to be bothered participating in a survey at the end of a long day at an
amusement park. - There are several potential answers. Incorrect Response Bias. The chosen participants might not want to
admit to being scared in front of the young lady. Questionnaire bias. The question is definitely worded in
a manner that would encourage participants to answer in a particular way. This is also systematic sampling
and someone used their judgment that only boys should be surveyed. A case could also be made for incorrect
sampling frame as no girls or other age groups have a chance of being represented. All of these examples also
eliminate the opinions of those in the park who do not choose to ride.