A study that randomly chooses participants and then assigns a treatment by chance calls for two different checks. Random sampling sets whose results the sample can represent; random assignment supports a causal claim. Trace the sampling list before extending a result to a larger population. Finally, distinguish a higher average from an increase for every person.
Hints
- Hint 1
A random sample can represent the complete list it came from, but not people who were never on that list. Who could the generator have picked in this study?
- Hint 2
Random assignment decides who gets the reminders after students are selected. Since chance, not students' tutoring habits, split the groups, what does their comparison let you say about cause?
- Hint 3
A higher average describes a difference between groups, not what happened to each person. Does the reported comparison support a claim about every student?
Step-by-step
Check sampling, assignment, and averages
Step 1Find the population the sample represents
No Desmos needed. The question asks what the study supports, not for a calculation. The researcher picked students at random from a complete list of ninth graders in the district's public high schools. A random sample can represent the list it came from, so the result can reach those ninth graders. It can't reach students in other grades.
- Step 2
Decide whether the difference can show cause
At each represented school, the researcher randomly assigned selected students to receive reminders or no reminders. This is random assignment: chance chooses the groups, making preexisting differences less likely to explain a gap between them. So if their averages differ, the study supports a causal claim about the reminders, not only an association.
- Step 3
Match the conclusion to the reported result
The reminder group averaged sessions, compared with for the no-reminder group during the same weeks. Since is greater, the reminders caused a higher average attendance. An average does not mean every student attended more sessions. For ninth graders in the district's public high schools, the supported conclusion is a causal increase in average tutoring attendance over those weeks. Choice C.