A school district has 24 public high schools. A researcher used a random number generator to select 300 ninth-grade students from a complete list of all ninth-grade students enrolled in the district's public high schools. At each school represented in the sample, the researcher randomly assigned approximately half of the selected students to receive a text-message reminder before each available tutoring session for 4 weeks. The other selected students received no reminders.
During the 4 weeks, the students assigned to receive reminders attended an average of 5.1 tutoring sessions, whereas the students assigned to receive no reminders attended an average of 4.3 tutoring sessions.
Which choice states the strongest conclusion supported by the study?
For questions about studies, locate the population from which the sample was randomly selected and locate whether participants were randomly assigned to treatments. Random sampling supports generalization to the sampled population, while random assignment supports a cause-and-effect conclusion. Then make sure the conclusion is limited to the correct population and describes an average effect rather than a guaranteed result for every individual.
Hints
Separate the two random processes
Determine what the random selection of students tells you, then determine what the random assignment of reminders tells you.
Check the population carefully
The list used for sampling included only ninth-grade students at the district's public high schools. Do not extend the conclusion to students outside that group.
Check the strength of the claim
The study compares group averages. Consider whether a conclusion about every individual student is justified.
Desmos Guide
Use study-design reasoning instead of graphing
Desmos is not useful for determining whether a study supports causation or identifying the population to which results can be generalized. Identify random sampling to determine the population and random assignment to determine whether a causal conclusion is justified.
Step-by-step Explanation
Identify the population represented by the sample
The researcher randomly selected students from a complete list of all ninth-grade students in the district's public high schools. Therefore, the study's results can be generalized to ninth-grade students in those schools.
Identify what allows a causal conclusion
The researcher randomly assigned sampled students to receive reminders or no reminders. Because the groups were formed randomly, the difference in their average attendance can be attributed to the reminders.
Match the conclusion to both features
The supported conclusion must state a causal effect, apply to ninth graders in the district's public high schools, and describe a difference in averages. Choice C meets all three requirements.