Studies confirm the correlation between the presence of a gene called apolipoprotein E and a brain disorder called Alzheimer’s disease. We know, however, that there are people without this gene who develop  Alzheimer’s disease and that some people with this gene do not develop Alzheimer’s disease. So there is no causal connection between the presence of apolipoprotein E and  Alzheimer’s disease. 

Which one of the following most accurately describes a reasoning flaw in the argument above?

A – The argument presumes, without providing evidence, that Alzheimer’s disease is caused solely by the gene.

B – The argument makes a generalization based on an unrepresentative sample population.

C – The argument mistakes a cause for an effect.

D – The argument ignores the possibility that not all that have the gene may have it expressed in their lifetimes. 

E – The argument presumes, without providing warrant, that correlation implies causation.

OA: D

Explanation : The argument says that while there seems to be a correlation between the presence of a particular gene and  Alzheimer’s disease, there are cases where the gene is present and people don’t get the disease and there are cases where people get  Alzheimer’s disease but do not have the gene. The problem here is two fold, one, X can cause Y without being the only cause for Y. E.g. drinking heavily can cause liver damage, but other behaviours can also cause the same (e.g. drug use). Secondly the author argues that ‘presence’ of the gene to be exhaustive. There might be cases where the gene is present but not expressed. 

A – The argument actually does not state this and states the opposite; that Huntington’s is not a cause. 

B – This is vague and does not clearly apply to the argument at hand. 

C – The argument does the exact opposite and makes it clear that there is no cause. 

D – This is exactly what the flaw is since ‘expression’ of the gene might be the pivotal factor. 

E – Similar to Option C this is not what the argument does. 

X

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