A social worker surveyed 200 women who recently had given birth to the

Question

A social worker surveyed 200 women who recently had given birth to their first child. Half of these women had chosen to give birth in a hospital or obstetric clinic; the other half had chosen to give birth at home under the care of certified midwives. Of the 100 births that occurred at home, only five had presented any substantial complications, whereas 17 of the hospital births had required extra attention because of complications during delivery. The social worker concluded from this survey that the home is actually a safer environment in which to give birth than is a hospital or clinic.

Which of the following, if true, most seriously calls the social worker's conclusion above into question?

(A) All of the women in the study who were diagnosed as having a high possibility of delivery complications elected to give birth in a hospital.

(B) Many obstetricians discourage their patients from giving birth in their own homes.

(C) Women who give birth in their own homes tend to experience less stress during labor and delivery than do those who deliver in hospitals.

(D) Women who give birth in hospitals and clinics often have shorter periods of labor than do those who give birth at home.

(E) Pregnant doctors prefer giving birth in a hospital.

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sanjitscorps18 · Answer

5 at home deliveries had issues
17 deliveries at hospitals had issues

Conclusion - Home deliveries are safer due to their environment

What would most seriously call the social worker's conclusion above into question

(A) All of the women in the study who were diagnosed as having a high possibility of delivery complications elected to give birth in a hospital.
 --> This provides a reason to not believe the social worker as the pregnant women profiles for hospital and home are completely different. If the hospital caters to deliveries with high possibility of complications, then it is most likely that it would have more numbers of deliveries that had complications.

(B) Many obstetricians discourage their patients from giving birth in their own homes.
--> Advice from obstetricians does not make home deliveries unsafe as is indicated by the premise

(C) Women who give birth in their own homes tend to experience less stress during labor and delivery than do those who deliver in hospitals.
--> This strengthens the argument

(D) Women who give birth in hospitals and clinics often have shorter periods of labor than do those who give birth at home.
--> Post delivery timelines for recovery are not the consideration of this argument

(E) Pregnant doctors prefer giving birth in a hospital.
--> This can coexist with the argument and still not weaken it.

IMO Option A

RonPurewal · Answer

This is a "correlation vs. causation" problem. The stated facts describe a statistical  CORRELATION  or  CORRESPONDENCE  (home births correlate with lower risk of birth complications; hospital births correlate with higher risk)—but then the passage goes on to conclude that there's a CAUSAL mechanism (the hospital environment CAUSES the additional complications because it's less safe; the home birthing environment CAUSES fewer complications because it's safer).

Correlation/causality is one of *vanishingly* few CR problem types on which the solutions follow a reasonably compact "formula" / "template":
 If x thing CORRELATES with y thing, then there are 3 (or 4) possibilities:
 • x causes y
 • y causes x
 • some other thing causes both x and y
  (ONLY IF X AND Y ARE SINGLE DATA POINTS)  • there's no causal relationship at all, and the co-occurrence is merely a random coincidence

To  STRENGTHEN  one of these possibilities as a conclusion,  rule out / disprove  any others that may be plausible. (One or more of these possibilities may be ridiculous/unreasonable/implausible, just by basic common-sense considerations like time order.)

To  WEAKEN  one of these possibilities as a conclusion, present evidence  FOR  one of the other ones.

.

In this case, the argument takes the correlation to mean that the birthing environment (x thing) CAUSES the differential risk level (y thing).

This conclusion is weakened if Women with different underlying obstetric risk levels (y thing) CHOOSE a birthing environment that's appropriate to those levels (...causes x thing), as in choice A.

.

WRONG ANSWERS:

B is irrelevant because it doesn't differentiate Mothers by risk level. (If choice B had said that obstetricians warn Women with   high-risk   pregnancies against giving birth at home, then it would be another way of expressing "y causes x" and therefore would be a correct answer.)

C essentially just repeats the given correlation, since "fewer complications" goes hand-in-hand with "less stress". This choice doesn't provide any additional insight into  which method of causation  is at work here, so it's irrelevant.

D is irrelevant because length of labor is not analyzed in the study at hand (only the frequency of actual complications is).

The Women's job fields are not included in the study data, so E is irrelevant as well.

Bunuel · Answer

KAPLAN OFFICIAL EXPLANATION:

Here's a very typical example of how surveys appear in GMAT Critical Reasoning. A social worker surveys 100 women who chose to give birth in a hospital, and 100 who chose to have their babies at home. The social worker concludes that the home is the safer environment in which to give birth, based entirely on the fact that in the sample studied, there were more cases of complications in the hospital. She assumes that the environment was responsible for the number of complications, and overlooks any other possible reason for the survey results. (A) weakens the argument by providing such an alternate reason for the statistical disparity: Women who were at high risk for complications all decided to give birth in a hospital. In other words, the study was skewed; the women in the two groups (the 100 who gave birth in the home and the 100 who gave birth in the hospital) were not equally likely to have complications to begin with.  (A) is correct.

An 800 test taker scrutinizes the sample groups used in surveys presented in Critical Reasoning questions, looking for disparities in the data or characteristics of the groups involved that may invalidate the survey.

(B) and (E) both make inappropriate appeals to authority—the fact that many doctors prefer hospital births alters neither the results of the study nor the conclusion drawn from these results.

An 800 test taker is not fooled by appeals to authority. She knows that conclusions must be backed up by solid evidence, not by the opinions or actions of experts.

(C) provides the opposite of what we're looking for—it strengthens the argument by providing a possible reason why home births are safer.

(D) The point at issue is where it's safer to give birth, not the respective labor times. Since there's no evidence that shorter labors are safer labors, (D) doesn't weaken the argument.

A social worker surveyed 200 women who recently had given birth to the

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GMAT Critical Reasoning (CR) Questions

A social worker surveyed 200 women who recently had given birth to the

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