In a certain wildlife park, park rangers are able to track the movements of many rhinoceroses because those animals wear radio collars. When, as often happens, a collar slips off, it is put back on. Putting a collar on a rhinoceros involves immobilizing the animal by shooting it with a tranquilizer dart. Female rhinoceroses that have been frequently recollared have significant lower fetility rate than uncollared females. Probably, therefore, some subtances in the tranquilizer inhibit fertility.
Inevaluating the argument, it would be most useful to determine which of the following?
a. Whether there are more collared female rhinoceroses than uncollared female rhinoceroses in the park.
b. How the tranquilizer that is used for immobilizing rhinoceroses differs, if at all, from tranquilizers used in working with other large mammals.
c. How often park rangers need to use trangquilizer dart to immobilize rhinoceroses for reasons other than attaching radio collars.
d. Whether male rhinoceroses in the wild park lose their collar any more often than the park's female rhinoceroses do
e. Whether radio collar is the only pratical means that park rangers have for tracking the movements of rhinoceroses in the park.
I have no doubt about the correct choice because it exploits the flaw in the argument.
But I still have a doubt about choice A.
The author makes a comparison between the fertility rates between 2 groups to support his conclusion. If there are 1000 recollared rhinos and 10 uncollared rhinos, and the fertility rates are 50% and 80% respectively, so we have 500 fertile recollared rhinos and 8 fertile uncollared rhinos.
if the difference between numbers of the two groups are too large-- i.e. 1000 and 10 -- and if we accept the author's assumption that the only purpose to shoot rhinos with T darts is to put collar, does the comparison between the fertile rates support the conclusion?
I must ask the question because before I see the correct answer I did not know the flaw of the argument, and the choice A seems good to me. So, if I know the answer for the question, I can eliminate choice A.
- Radio Collar (R.C) enables Tracking.
- R.C -> tranquilizing (T)
- More R.C -> lower Death Rare (Causal relationship)
- More Fertility -> Less Death
- Notice the gap between the premises (Death Rate-DR) and (Fertility-F)
- Hence we should deduce correlation, and more specifically causality
- But in what direction? does DR->F or F->DR
- Well, logically F->DR makes sense, the other way does not make sense
- Tranquilizer (a material in it) -> more fertility
A. This comparison have nothing to do with the assumption or conclusion- and hence not relevant.
B. Again, This comparison have nothing to do with the assumption or conclusion.
C. Sounds good - lets try to weaken & strengthen the conclusion by taking 2 extreme cases:
- Now, look at the structure again:
- More Tranq. -> More Fertility -> Less death
- a good way to understand the implications of an answer choice is by taking a specific example and analyze its impact.
- So if other uses CAUSE Tranq. ( something else -> Tranq) - for example pregnancy, then we are weaken the relationship "More Tranq.->More Fertility". why? because Fertility->Pregnancy->Tranq.
- Now if we negate that option, we have in fact negated an alternate weakener - which strengthen the conclusion.
Hence C is correct,
D.The sample group (males) is not relevant, as is the comparison.
E. Assume with have another practical means- this does not weaken the conclusion.