For a survey asking who a result can describe, compare the research goal with the sampling frame, the list of people eligible to be picked. Random selection helps a sample represent that list, not anyone left off it. Check who could be chosen before trusting a conclusion that reaches a larger population because the pick was random.
Hints
- Hint 1
The target population is the whole group the researcher wants to describe, not necessarily everyone she contacts. Find the group named in her goal. Whose sleep hours does she hope to estimate?
- Hint 2
The sampling frame is the list from which names are picked. Someone missing from that list has no chance of being chosen. Who was eligible to appear on this roster?
Step-by-step
Find the limit of the sample
Step 1Identify the group she wants to describe
No Desmos needed. A calculator can't tell who was eligible to be picked.
The researcher wants to estimate sleep for teenagers across her state. That group is the target population, the people she hopes to describe. Wanting a statewide estimate doesn't mean her sample represents the whole state.
- Step 2
Find who could be selected
Her roster lists students at her own high school. The sampling frame is the list names are picked from, so teenagers at other schools had no chance of appearing in this sample.
- Step 3
Apply the limit of random selection
She randomly picks names from that roster. Random selection helps a sample represent the group it came from; it doesn't add teenagers from other schools. A random sample can support an estimate only for the population that had a chance to be picked. So the study can estimate average sleep for students at her high school, not for all teenagers in the state. Choice B.