a The location where a survey is conducted may cause a sample to be biased.
B
b How can the time of day introduce bias in a sample?
C
c A sample is biased when it is not representative of the population.
D
d Consider the location where a survey is conducted.
A
a No, see solution.
B
b No, see solution.
C
c No, see solution.
D
d Yes, see solution.
Practice makes perfect
a We are writing an article about the support of town residents for the proposal for new bike paths.
We want to collect data — showing the opinion of town residents — that will be presented in the article. To do so, let's consider the given data collection method.
Every tenth person leaving a bicycle repair store is surveyed.
Since we survey every tenth person, it is a systematic sample. However, only people who are visiting a bicycle repair store are able to respond to the survey. These people are more likely to ride a bike regularly and would benefit from the proposal. Therefore, this sample will introduce bias.
b Similar to Part A, we will determine whether the data collection method will result in an unbiased sample. Let's consider the given situation.
You call homes in your neighborhood every morning Monday through Friday for one week.
When calling homes in the morning, a lot of residents may be at work or school. Then the sample would not be representative of the population of the residents in our neighborhood. Therefore, the sample is biased.
c Just as in Parts A and B, let's consider the given situation.
You send an e-mail to 100 classmates chosen at random.
We can see that this is a random sample, which is often unbiased. This time, however, the sample is not representative of the population of town residents because we survey only our classmates. It means that the sample is biased.
d Just as we did in the previous parts, we will determine whether the data collection is unbiased. To do so, let's consider the given situation.
You poll every fifth person at a popular local sandwich shop.
Similar to Part A, this is a systematic sample. Since the local shop is popular, we can assume that any random resident will visit the shop and that the sample is representative of the population. Therefore, the sample is unbiased.
