AP Stats Unit 3 FRQ Practice Prompt Answers & Feedback

FRQ Unit 3 Exam Practice Prompt

• a. Was this study an experiment or observational study? Justify your decision.

• b. After the study, it was determined that the group that received the new medication showed levels of improvement that were statistically significantly higher than the group that received the placebo. Based on this result and the design of the study, would the researchers be justified in claiming that the new medication could be useful in helping individuals similar to those in the study overcome any of their fears?

• c. A newspaper article that summarized the results of the study mentioned that it was done in a “double-blind fashion.” Explain what that means in the context of this study.

FRQ Writing Samples and Feedback

FRQ Practice Submission 1

In part (a), it appears that you’ve mixed up the purpose of random selection (which is not present in the scenario, as you mention) and random assignment (which is present in the scenario). Random ASSIGNMENT (of treatments) is the key distinguishing factor between an experiment and observational study; therefore this scenario is in fact an experiment. However, since there is not random selection, we would not be able to generalize the results of the experiment to other fear types, so we would still say “no” in part (b), but for a different reason. Because your reasoning in part (b) is consistent with your response in part (a), you would still likely be able to earn at least partial credit in part (b), though part (a) would be marked incorrect. Your response in part ( c ) is spot-on, and includes a benefit of blinding. It would earn “E”

FRQ Practice Submission 2

Your response is very solid!

In part (a), you make it clear which treatments were assigned (“new medication or a placebo pill”) which correctly answers the question and includes context of the problem. This would earn “E” (full credit)

In part (b), your answer of “no” is correct but your explanation for why is not all the way there. You mention that there is not random selection, but then state that this implies we cannot determine causation. That is an incorrect statement: we can determine causation due to the random assignment of treatments. In this case, the fact that we’re lacking random selection means that we cannot generalize the results of the study to a larger population beyond those who were involved in the experiment. Additionally, the question mentions “any fears,” but this experiment specifically dealt with volunteers with a specific fear (arachnophobia). So the volunteers would not be a representative sample (which is made “worse” by the lack of random selection). Therefore, your response will either earn “P” (partial) or “I” (incorrect), depending on the rubric for that year (since this is a made-up question I can’t say for sure, some rubrics are more “generous” than others)

In part ( c ), you give a strong description of the meaning of “double-blind” and include appropriate context from the scenario. This would earn “E” (full credit).

FRQ Practice Submission 3

In part (a), you clearly justify why this is an experiment, including a description of assigned treatments. “E” for this part.

In part (b), you explain why we cannot generalize beyond this group of volunteers, showing a clear understanding of the difference between random selection and random assignment. “E” here as well.

Finally, in part ( c ), you give a clear description of “double-blind” in the context of this study. "E"s all around! Nicely done.

FRQ Practice Submission 4

In part (a), you clearly describe why this is an experiment (“a treatment (the pill) was given…”), including context from the scenario. Be careful with saying “because there was treatment” - you make it sound like the pill was the only treatment assigned, when there were in fact two treatments assigned - the pill and the placebo. On some rubrics that would be enough to knock you down from “E” (full credit) to “P” (partial credit)

In part (b), you will not earn credit. Random assignment was used in this experiment, but since the people participating were volunteers with one specific fear, we cannot assume that they are representative of the larger population of people with any fear. Random selection of individuals could have allowed this generalization to happen.

In part ( c ), you give a correct description of what “double-blind” means in the context of this study, though your second sentence is a bit vague: “the treatment does not change.” You may be referring to the idea that we blind participants to their treatment so that their behavior within the experiment does not change; once they are assigned their treatments, the treatment itself would not change. You would likely earn credit for your response, but be careful with the precision of your descriptions.

FRQ Practice Submission 5

I have less feedback for this response… but that’s because you did very well! In part (a), you give the correct answer, with a correct reason in context (assignment of the specific treatments). In part (b), you explain that “volunteers” will limit our scope of inference, and in part ( c ) you clearly explain what blinding is and it’s purpose in the context of this study. Well done!

FRQ Practice Submission 6

In part (a), you correctly choose “experiment” and clearly connect this to the assignment of the treatment. However, you only mention one treatment being assigned, when there was also a placebo assigned - which also counts as a treatment. Be sure to say something like “since the volunteers were assigned either the medication or the placebo”.

In part (b), you explain that volunteers cannot be used to generalize to a larger population, even mentioning that there may have been selection bias. Good work.

In part ( c ) , you give a concise and correct description of being “double-blind,” in context. Well done!

FRQ Practice Submission 7

Your responses are thorough and in-context for all three parts. In part (a), good job naming the treatments that were assigned as a part of your justification. In part (b), you correctly connect the scenario to volunteers; in part ( c ) you correctly define double-blinding. Nicely done!

FRQ Practice Submission 8

Perfect on all three parts!

FRQ Practice Submission 9

Nice answers! Part (b) gives a good reason but may need to be explained a little more (“volunteers with fear of spiders, meaning that those people would not be representative of the larger population described”) or something like that. (a) and ( c ) gives an appropriate level of context for your answers.

FRQ Practice Submission 10

Good work on all three parts - clear, descriptive responses in context of the scenario. Should earn full credit.

FRQ Practice Submission 11

Solid work!

In part (a), you give a correct reason for “experiment” using in-context descriptions of the treatments.

In part (b), you give the correct answer (“no”), but don’t give the correct reason for why we cannot apply the results to the population. In our case, the sample is not representative of the population (volunteers with one specific fear cannot represent the population of people with all fears). We could do an inference procedure here… but because our sample is not representative, it would provide meaningless results.

In part ( c ), you give a good description of the meaning of “double-blind,” including a reason for doing so. Well done!

FRQ Practice Submission 12

Nice job! Your answers are short, but contain all appropriate information that would show readers that you understand. You should earn full credit.

FRQ Practice Submission 13

In part (a), you give an appropriate reason for “experiment” (naming treatments in context). Nice job.

In part (b), be careful. A well-designed experiment allows us to make explicit cause-and-effect conclusions based on treatments, but does not necessarily allow us to generalize beyond those in the study… we can only do that if the experimental units are representative of a larger population. In this scenario, precisely because the volunteers explicitly had one specific fear, we cannot generalize the results to people with any fear.

Part ( c ) is well done.

FRQ Practice Submission 14

In parts (a) and (b), you give the correct answers but ended up saying a little too much - potentially jeopardizing full credit. For part (a), you correctly mention random assignment of medicine/placebo as the reason for this being an experiment, but then go on to say that “this study has a control group.” That is true, but just having a control group does not guarantee that any particular scenario is an experiment; your answer makes it sound like it does. That could be enough to deduct. Then in part (b), you correctly identify that we can’t generalize from people with arachnophobia to people with any fear, but also comment on the sample size. Small samples - when randomly selected - can be representative of populations from which they come, so that by itself isn’t a good reason to say no (the better reason is what you mentioned about the specific fear). You seem to be going for the explanation that there wasn’t random selection, but it doesn’t come across quite as cleanly as you may have wanted. In part ( c ), you give a correct explanation of double-blind. No issues there. :)  

FRQ Practice Submission 15

Strong responses! All three parts include appropriate information, in context. I also appreciate the phrase “giver of pill people” and may or may not borrow it in the future, lol