19. This LSAT weaken argument question contains causality -- the Analyst assumes that the only cause for the disproportionately low number of non-research biology professors is the bias held by university administrators. To weaken this argument, seek a choice that provides another possible cause. (B) does this by providing the possibility that the disproportionately lower number is caused by something to do with being a biology professor (since both research and non-research biology professors fill a disproportionately low number of administrative positions), and not the university administrators' bias.

(A) makes a comparison between scientific and nonscientific, but the argument's scope is limited to scientific only.

(C) refers to the total amount of grant money, and that biology professors get more of it. If anything, this seems to strengthen the argument by eliminating a competing cause by hinting that it's the amount of grant money that a professor receives does not cause his or her appointment to a scientific administrative position.

(D) explains a possible cause for why some biology professors choose not to pursue research, but we need a choice that provides a cause for why a disproportionate number fill scientific administrative positions.

(E) has no effect. If (E) stated that biology professors held their professorships (not administrative positions) for a shorter time, then this might be alternate cause, because if they held their professorships for less time, then they presumably be less likely to be appointed to an administrative position.

 

20. This LSAT assumption question works this way:

	P1: Found that some high b.p. cases effectively treated with meds
	P2: Treat a stress-caused illness g Reduction of stress
	_______________________
	C: Some cases of high b.p. not caused by stress

The Researcher assumes that the medicine does not indirectly reduce stress, which would then in turn treat high blood pressure. Negate (E) by removing "does not itself". This negation of (E) clearly weakens the argument and thus (E) contains a required assumption.

(A) refers to a correlation but none is stated or implied in the argument. The argument tells us that high b.p. is caused by stress, but just as correlation does not imply causation, causation does not imply correlation. Also, the second premise tells us that the treatment of high b.p. requires the reduction of stress. But, again, there's no correlation implied. The contrapositive of the second premise is this:

Reduction of stress g Treat a stress-caused illness

Not this:

Reduction of stress g Treat a stress-caused illness

Nor this:

Reduction of stress by X amount g Treat a stress-caused illness by correlated Y amount

Nor this:

Reduction of stress by X amount g Reduce blood pressure by correlated Y amount

 

(B) confuses sufficient and necessary conditions of the second premise, plus includes "can at times" and "lower". The second premise states that treatment of high b.p. requires reduction of stress, but this does not imply that reduction of stress will result in treatment of high b.p. Also, we don't know for sure whether treating high b.p. consists of lowering b.p. Perhaps only the symptoms are treated.

(C) refers to the interaction between reduced stress and high b.p. medicine. This might explain how the generally accepted belief came about, but this is not a required assumption for the author's conclusion. Also, the argument does not state whether or not the "some" cases treated effectively with meds were also treated by the reduction of stress at the same time, and thus (C) is irrelevant.

(D) provides a dichotomy -- either meds or reduce stress. No such dichotomy is needed for the author's conclusion, which allows for high b.p. to be treated by meds or stress reduction. Also, (D) states "some" conditions, which may not include high b.p.

 

21. This LSAT error question works this way:

	P1: Different historians never arrive at same conclusion
	_______________________
	C: Historians never determine actual events

Ignore everything after the semi-colon in the second sentence.

Catmull fails to recognize that a historian could arrive at a correct conclusion, even though noone else arrives at that same conclusion, and (B) is the correct choice.

(A) refers to circular reasoning, however the conclusion and premise are different statements.

(C) refers to value, which is not part of the argument. The argument is concerned with whether or not historians determine truth, and thus "value" is irrelevant.

For (D), there's only one premise and thus no possible contradiction.

(E) refers to confusing sufficient and necessary conditions, which is not the error.