SamuelWitwicky wrote:
Mike, you are like Bunuel for Quant. Anyway, I feel embarrassed to say this, but I chose B because I thought since the manufacturing process now prevents contamination of SV40, surely this virus must have caused a problem (i.e. contributed to mesothelioma). Why else would you change the manufacturing process unless SV40 caused problems right? Therefore, it would be sufficient as an assumption. I know E is definitely the better answer, but what do you think of my reasoning for B?
Dear
SamuelWitwicky,
I'm happy to respond.
Thank you very much for you kind words. I must say, I feel a little humbled by the comparison to Bunuel, whom I hold in tremendous respect.
What you ask is an excellent question. Here's the prompt again:
Although exposure to asbestos is the primary cause of mesothelioma, a slow-developing cancer, researches believe that infection by the SV40 virus is a contributing cause, since in the United States 60 percent of tissue samples from mesotheliomas, but none from healthy tissue, contain SV40. SV40 is a monkey virus; however, in 1960 some polio vaccine was contaminated with the virus. Researches hypothesize that this vaccine was the source of the virus found in mesotheliomas decades later.
Which of the following, if true, most strongly supports the researchers' hypothesis?
(A) SV40 is widely used as a research tool in cancer laboratories.
(B) Changes in the technique of manufacturing the vaccine now prevent contamination with SV40.
(C) Recently discovered samples of the vaccine dating from 1960 still show traces of the virus.
(D) In a small percentage of cases of mesothelioma, there is no history of exposure to asbestos.
(E) In Finland, where the polio vaccine was never contaminated, samples from mesotheliomas do not contain SV40.Here's what I think about
(B). The hypothesis is that the contamination of the polio vaccine with the virus SV40 contributes to the incidence of mesothelioma. We don't know whether this is true: the researcher think that this is true, and we are asked to strength this conclusion.
If that conjecture were true, then it would be a problem, and
(B) would be an excellent solution to the problem. But we are not asked to solve the biological problem discussed: we are asked to strengthen the conclusion. Furthermore, we don't have any additional information. The prediction of the researchers would be that if we changed the vaccine manufacturing technique, eliminating SV40 contamination, then we would expect the incidence of mesothelioma to drop. If we were told all this, then that would be incredibly strong evidence for this conjecture. The problem is: we are not told the result. We are told only that SV40 has been eliminating from the vaccine manufacturing process. Then what happened? Frustratingly, we are not told. The results of this change could be a huge strengthener, but we are not told this. That's the problem with
(B).
We can't really make inferences from the manufacturer's motivations. First of all, when a group of scientists speculate that some X is a risk, a lot of people just start avoiding X because it could be a risk, even though sometimes it turns out that this X is perfectly safe. The manufacturers might have caught wind of the scientists' speculation and simply believed them because they are scientists, irrespective of the validity of the conjecture. Furthermore, it is quite likely that the manufacturer made a change that eliminates not just SV40 in particular, but a number of viruses --- for example, some kind of intense heat or flash pasteurization, something that would destroy virtually all viruses. The manufacturers could have made this change on general principles, without any knowledge at all about SV40 in particular. We simply don't know.
Does all this make sense?
Mike