Question 52·Easy·Evaluate Statistical Claims: Observational Studies and Experiments
A city planner emailed a survey to 300 residents randomly chosen from those who commute by bicycle at least twice a week. The survey asked whether they would support adding protected bike lanes downtown. Of those surveyed, 88% said they would support the addition.
Which of the following inferences is most appropriate based on these results?
For SAT statistics questions about inferences, first identify exactly who was in the sample and whether the sample was random; you can only generalize to a population that matches that sampled group. Next, check if the study was an experiment (with random assignment of a treatment) or just an observational survey—only experiments justify cause-and-effect language. Finally, eliminate any answer choices that (1) talk about a different or broader group than the sampled population or (2) claim that one variable “caused” another when the design does not support that conclusion.
Hints
Focus on who was surveyed
Look closely at the description of how the 300 residents were chosen. From which specific group of residents were they randomly selected?
Match the population to the answer choices
Compare that group to the groups mentioned in the answer choices. Which choices talk about the same type of people, and which ones talk about different groups?
Think about what kind of study this is
Was this an experiment where something was changed or assigned to people, or just a survey asking for opinions? That will affect whether you can talk about cause and effect.
Check for overgeneralization
Ask yourself: does this choice go beyond what the data supports—for example, claiming something about people who were never surveyed or about the entire city?
Step-by-step Explanation
Identify who was actually sampled
Read the first sentence carefully: the 300 residents were randomly chosen from those who commute by bicycle at least twice a week. That means:
- The sample is 300 frequent bicycle commuters.
- The population you can generalize to is all residents who commute by bicycle at least twice a week, not all residents in the city and not people who commute by car.
Interpret the numerical result
Of those surveyed, 88% said they would support adding protected bike lanes downtown.
- 88% is well over half, so it is reasonable to describe this as “most” of that group supporting the lanes.
- Because the sample was random within that group, it is appropriate to extend this “most” to the whole population of frequent bicycle commuters in the city.
Check which answer choices match the population you can generalize to
Now compare each option to the actual population you can make an inference about:
- Any answer about all city residents goes beyond the sampled group.
- Any answer about people who commute primarily by car is about a completely different group from the one sampled.
- An answer that talks about cause and effect (what would “cause” people to do) would require an experiment, not just a survey.
Match the correct inference to the study
The only option that:
- Stays within the correct population (residents who commute by bicycle at least twice a week), and
- Makes an appropriate, non-causal inference from a random sample (saying that “most” of that group would support)
is:
Most residents who commute by bicycle at least twice a week would support adding protected bike lanes downtown.