QUESTION TEXT: A study of the dietary habits of …
QUESTION TYPE: Flawed Reasoning
CONCLUSION: Galactose causes cancer, if you have more of it than you can process.
REASONING: There are two groups, one with cancer and one without it. Each group ate a similar amount of Yogurt, which has galactose. The cancer group didn’t have enough enzyme to process galactose.
ANALYSIS: This question makes a causation-correlation error. The fact that two things happen together doesn’t mean one causes the other.
The group already had cancer. Maybe their cancer lowered their production of the enzyme. Then cancer would be the cause of galactose malabsorption, and not the reverse.
Or maybe a third factor causes both cancer and the reduction in the enzyme.
___________
- This sounds tempting, but it’s not necessary. Read carefully. It asks whether:
1. Everyone’s diet
2. was exactly the same
3. in all other respectsNo medical study meets this standard. It’s impossible. People’s diets are very different. A study can still tell us something, even if not every variable is controlled with perfect accuracy. - The argument is just making a claim about galactose. It doesn’t have to make practical recommendations to improve people’s lives.
- The argument doesn’t have to describe every possible cause of cancer. There are thousands of causes. The argument didn’t say that galactose is the only cause of cancer.
- CORRECT. If cancer causes low enzyme levels, then galactose malabsorption is an effect of cancer, not a cause.
- The groups were presumably somewhat large. If one person in a group lacked the enzyme, that shouldn’t affect the overall study.
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Paul says
I ended up getting this question right because D was the only one that COULD be correct, but I think the writers were sloppy in writing the stimulus, as it’s ambigious as to whether the study was retrospective or rather a 5-year long study.
Because in one case, the five-year study case, then the low level of the enzyme was detected PRIOR to the cancer diagnosis, taken while the study was merely keeping track of everyone’s dietary habits and enzyme levels for evaluation later when some members of the study inevitably developed cancer after the five-year study period.
On the other hand, (and this is apparently the correct interpretation) the study was entirely retrospective, the groups selecting for people who had recent cancer diagnoses, then yes the lack of enzyme would merely be a present correlation, meaning D is correct.
While answering the question I had to pause and consider whether this was supposed to be a trick answer or not — after all, if it was a five year study, and the low enzyme level was pre-existing in what turned out later to be the cancer group, then answer D would just be plain wrong because the enzyme deficiency predated the cancer diagnosis.
Luckily, because none of the other answers really made sense, I chose D and got it right, but I wish LSAC wouldn’t leave ambiguities like that in their question stimulus.
FounderGraeme Blake says
Those are good observations, but the question actually addresses this. It says a study examined two groups. One group with a recent cancer diagnosis, the other without. Then the studies examined their diets in the previous five years.
It would be very hard to examine two groups and split them into a cancer and non cancer group: cancer is rare.
In any case the LSAT doesn’t really do trick questions in this way, especially not in the first ten questions. And they tend to avoid ambiguity. Perhaps I’m mistaken but I think the way this is written the study could only be retrospective. The LSAT expects people to know about control groups but not about the difference between retrospective vs. ongoing studies.
Note: This is an old comment but I wanted to clarify the point.