Researchers wanted to investigate the relationship between receiving a free public-transit pass and school attendance among 11th-grade students in a school district. From a complete roster of all 11th-grade students, the researchers randomly selected 600 students.
Using school records, the researchers found that 176 of the selected students had received a free public-transit pass through a community assistance program during an 8-week period. The researchers also recorded each selected student's mean number of school days attended per week during that period. Students who had received a transit pass had a greater mean number of school days attended per week than students who had not received a pass.
Which choice is best supported by the study?
For questions about studies, first determine whether the sample was randomly selected and whether treatments were randomly assigned. Random selection can support generalizing an observed pattern to the population, while random assignment is needed to support a cause-and-effect conclusion. State the conclusion no more broadly than the design permits.
Hints
Check the sample
Determine whether the selected students can represent the larger district population.
Check the group formation
Ask whether the researchers assigned students to receive passes or simply compared students based on an existing characteristic.
Separate association from causation
A study can show that two variables are related without showing that one variable caused the other.
Desmos Guide
Recognize that calculation is not needed
Desmos is not needed because the answer depends on the study design. Identify that the students were randomly selected, then check that they were not randomly assigned to receive transit passes.
Step-by-step Explanation
Identify the sampling method
The researchers randomly selected 600 students from the roster of all 11th-grade students in the district. Random selection supports generalizing a pattern found in the sample to the district population.
Identify how the groups were formed
The students were grouped according to whether they had already received a transit pass through an assistance program. The researchers did not randomly assign students to receive a pass or not receive one.
Limit the conclusion appropriately
The study supports an association: students who received passes had higher mean weekly attendance. Without random assignment, other differences between students who received passes and students who did not may explain the difference, so a causal conclusion is not supported.