Several studies have shown that hospitals are not all equally successful: patients are much more likely to die in som...

Naz September 1, 2015

Please disregard the question mark. Our development team is working on fixing that issue. It should read "per-patient."

Conclusion: the differences in the quality of care provided by hospital staff are probably responsible for the differences in mortality rates.

Why? We are told that several studies have shown that hospitals are not all equally successful, i.e. patients are much more likely to die in some of them than in others and that the hospitals in the studies had approximately equal per-patient funding.

Where's the issue? Well, we know nothing about the types of hospitals studied or about the types of patients at each hospital. For instance, if one hospital is for trauma and another is for outpatient clinics, then the hospital focused on trauma will have a higher proportion of deaths than the one focused on outpatient examinations. Regardless of the fact that the hospitals studied had approximately equal per-patient funding, the fact that the hospital focused on more emergency, near-death patients has more patients who die than any not focused on such severe issues shows that the former's difference in mortality rates is not necessarily due to a difference in quality of care provided by hospital staff.

This is exactly what answer choice (B) illustrates: "Patient populations vary substantially in average severity of illness from hospital to hospital."

So, as you can see, answer choice (B) casts the most doubt on the conclusion in the argument.

Hope that clears things up! Please let us know if you have any other questions.

Flavio March 2, 2016

@Naz is it fair to say therefore that B is an alternate cause to the mortality rates varying?

Mehran March 3, 2016

Hi @Flavio, thanks for your question. Yes, that is exactly right! Remember there are three ways to weaken a cause-and-effect argument: (1) present an alternative cause, (2) show the cause exists without the effect, or (3) show the effect exists without the cause. This question is an example of tactic 1.



Hope this helps! Please let us know if you have any additional questions.