a Is a sample representative of the population of students in our school? If not, the sample is biased.
B
b A survey question introduces bias if it contains assumptions or makes one answer seem better than the other.
A
a See solution.
B
b See solution.
Practice makes perfect
a We are given the information about a survey taken in our school. The survey is conducted to gather student opinions on the menu items offered by the cafeteria. We want to determine whether each of the given samples could introduce bias in the results.
Sampling Method
Biased?
Asking the nutrition club
?
Asking the boys' wrestling team
?
Asking 5 students from each homeroom
?
Let's consider the first sampling method. Members of the nutrition club may overrepresent some eating habits — they will most likely want to include lots of fruits and vegetables — which can influence the answer in the survey and cause bias.
Sampling Method
Biased?
Asking the nutrition club
Yes ✓
Asking the boys' wrestling team
?
Asking 5 students from each homeroom
?
Asking the boys' wrestling team is likely to have similar issues as the previous method. Since wrestlers usually need to stick to particular sports diets — which are typically high in protein — this sample is not representative of the population of the students. Additionally, girls also go to our school. This means that the sample could lead to biased results.
Sampling Method
Biased?
Asking the nutrition club
Yes ✓
Asking the boys' wrestling team
Yes ✓
Asking 5 students from each homeroom
?
Finally, let's consider the last sampling method. Because we ask 5 students from each homeroom, this will give a sample of students from each class. This is a stratified sample. Since we ask students from all grade levels without any assumptions, the sample will not introduce bias.
Sampling Method
Biased?
Asking the nutrition club
Yes ✓
Asking the boys' wrestling team
Yes ✓
Asking 5 students from each homeroom
No *
b We want to write a biased survey question that favors pizza as an item offered by the cafeteria. To do so, we need to make pizza seem better than other options. Let's take a look at an example question.
Biased Survey Question
Do you prefer delicious pizza or plain sandwiches in the school cafeteria?
Words such as delicious and plain suggest the answer and encourage respondents to favor pizza. Next, we will write an unbiased question about the cafeteria menu. Unbiased survey questions cannot contain any assumptions or make one answer seem better than another. Also, we will not limit the choice to only two items. Let's look at an example question.
Unbiased Survey Question
What menu choices would you enjoy having in the school cafeteria?
