Geographic Variation

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okigbo: Master | Next Rank: 500 Posts; Posts: 177; Joined: Sun Aug 02, 2009 9:39 pm; Thanked: 6 times

by okigbo » Mon Oct 19, 2009 11:08 pm

There is a great deal of geographical variation in the frequency of many surgical procedures - up to tenfold variation per hundred thousand people among different areas in the numbers of hysterectomies, prostatectomies and tonsillectomies.

To support a conclusion that much of the variation is due to unnecessary surgical procedures, it would be most important to establish which of the following?

a. A local board of review at each hospital examines the records of each operation to determine whether the surgical procedure was necessary

b. The variation is unrelated to factors (other than the surgical procedures themselves) that influence the incidence of diseases for which surgery might be considered

c. There are several categories of surgical procedures that are often performed unnecessarily

d. For certain surgical procedures, it is difficult to determine after the operation whether the procedures were necessary or weather alternative treatment would have succeeded

e. With respect to how often the are performed unnecessarily, hysterectomies, prostatectomies, and tonsillectomies are respective of surgical procedures in general

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Source: Beat The GMAT — Critical Reasoning | Mon Oct 19, 2009 11:08 pm

delhiboy1979: Master | Next Rank: 500 Posts; Posts: 239; Joined: Wed Feb 11, 2009 2:50 am

by delhiboy1979 » Tue Oct 20, 2009 2:09 am

a. A local board of review at each hospital examines the records of each operation to determine whether the surgical procedure was necessary
Does not support

b. The variation is unrelated to factors (other than the surgical procedures themselves) that influence the incidence of diseases for which surgery might be considered
Out of scope

c. There are several categories of surgical procedures that are often performed unnecessarily
Too general

d. For certain surgical procedures, it is difficult to determine after the operation whether the procedures were necessary or weather alternative treatment would have succeeded
Right answer - supports the conclusion

e. With respect to how often the are performed unnecessarily, hysterectomies, prostatectomies, and tonsillectomies are respective of surgical procedures in general
Don't even know what this implies

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Testluv: GMAT Instructor; Posts: 1302; Joined: Mon Oct 19, 2009 2:13 pmFollowed by: 164 members; Location: Toronto; Thanked: 539 times; GMAT Score:800

by Testluv » Tue Oct 20, 2009 7:21 am

The answer must be B.

The passage tells us that certain surgeries occur at differential rates across different regions. We need to find a choice that supports the conclusion that this difference in rates is not indicative of certain surgeries being performed unnecesarily.

So before approaching the answer choices, you should ask yourself: what other factor could account for the difference in rates? Then, you should answer yourself: maybe certain diseases occur more frequently in certain places.

Choice B matches this insight.

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Testluv: GMAT Instructor; Posts: 1302; Joined: Mon Oct 19, 2009 2:13 pmFollowed by: 164 members; Location: Toronto; Thanked: 539 times; GMAT Score:800

by Testluv » Tue Oct 20, 2009 8:00 am

While choice d is tempting, it would fail to explain why these surgical procedures occur at different rates.

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RadiumBall: Master | Next Rank: 500 Posts; Posts: 132; Joined: Thu Dec 02, 2010 2:49 am; Thanked: 5 times

by RadiumBall » Sat Feb 26, 2011 8:48 pm

I am not convinced at all. Can someone please explain why B is correct?

According to me we need to find a choice which says that the variations are indeed due to unnecesary surgical procedures.

Thanks

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David@VeritasPrep: GMAT Instructor; Posts: 2193; Joined: Mon Feb 22, 2010 6:30 pmFollowed by: 512 members; Location: Vermont and Boston, MA; Thanked: 1186 times; GMAT Score:770

by David@VeritasPrep » Sun Feb 27, 2011 2:34 pm

Radium - let's break this down.

This is from the OG 10 edition.

This is a special type of the strengthen question where the conclusion is in the question stem. Please be on the lookout for this as it occurs fairly regularly.

The conclusion is "much of the variation is due to unnecessary surgical procedures" This indicates a cause and effect relationship. We are, in effect, saying that the reason that there is a geographical variation in the listed procedures is because in the areas where more procedures are performed many of those procedures are not necessary.

Now there could be other reasons for a variation in the number of surgeries. For example, the new natural gas wells that are being drilled in people's back yards have been proven to contaminate the water supply and so it would be very reasonable to see additional cases of cancer and therefore additional procedures near these poisonous wells. So that would be another cause not unnecessary procedures, but variations in the toxicity of various places around the U.S. (or the world depending on how you read the question).

In order to strengthen a question that involves cause and effect, you will want to consider the possibility of blocking an alternate cause. In this case we are saying the cause is the "unnecessary procedures" so we want to block the things that would make these procedures necessary - like variations in the age of the population, the health of the people, the quality of the water, even the ability of the people to pay for the procedures.

Answer Choice B does this. It says, "The variation is unrelated to factors (other than the surgical procedures themselves) that influence the incidence of diseases for which surgery might be considered." So this blocks the idea that the cause of varying rates of procedures would be any of the factors (age, health, toxins) etc. mentioned above. So we strengthen one cause by blocking another.

Does that help you to think of approaching questions that feature a cause and an effect?

Last edited by David@VeritasPrep on Tue Apr 30, 2013 11:11 am, edited 1 time in total.

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RadiumBall: Master | Next Rank: 500 Posts; Posts: 132; Joined: Thu Dec 02, 2010 2:49 am; Thanked: 5 times

by RadiumBall » Sun Feb 27, 2011 8:52 pm

Sure it does...thanks a lot David.

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cyrwr1: Master | Next Rank: 500 Posts; Posts: 218; Joined: Sat Jul 24, 2010 2:43 pm; Thanked: 5 times

by cyrwr1 » Mon Feb 28, 2011 12:04 pm

Thanks for your explanation David.
Would it be possible for you to give us a few of these questions for practice and see if we can apply your method?

Thanks once again!

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akhpad: Legendary Member; Posts: 809; Joined: Wed Mar 24, 2010 10:10 pmFollowed by: 4 members; Thanked: 50 times

by akhpad » Mon Aug 08, 2011 3:04 am

Very good explanation from David.

The variation is unrelated to factors--other than the surgical procedures themselves--that influence the incidence of diseases for which surgery might be considered.

So, surgery is done based on unrelated factors of diseases. Hence it is unnecessary.

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a_new_start: Junior | Next Rank: 30 Posts; Posts: 16; Joined: Wed Feb 11, 2015 1:39 am

by a_new_start » Wed Feb 11, 2015 3:48 am

Nice explanation David.

It worked for me.

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RBBmba@2014: Legendary Member; Posts: 944; Joined: Wed May 30, 2012 8:21 amFollowed by: 5 members; Thanked: 8 times

by RBBmba@2014 » Mon Oct 05, 2015 11:36 am

Hi Verbal Experts - could you please share your DETAILED analysis for this CR ?

Much thanks!

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Ashish_Garg: Newbie | Next Rank: 10 Posts; Posts: 1; Joined: Mon Apr 04, 2016 8:39 pm

by Ashish_Garg » Mon Jun 27, 2016 7:08 am

Hi David can you tell me why option E is wrong.

David@VeritasPrep wrote:Radium - let's break this down.

This is from the OG 10 edition.

This is a special type of the strengthen question where the conclusion is in the question stem. Please be on the lookout for this as it occurs fairly regularly.

The conclusion is "much of the variation is due to unnecessary surgical procedures" This indicates a cause and effect relationship. We are, in effect, saying that the reason that there is a geographical variation in the listed procedures is because in the areas where more procedures are performed many of those procedures are not necessary.

Now there could be other reasons for a variation in the number of surgeries. For example, the new natural gas wells that are being drilled in people's back yards have been proven to contaminate the water supply and so it would be very reasonable to see additional cases of cancer and therefore additional procedures near these poisonous wells. So that would be another cause not unnecessary procedures, but variations in the toxicity of various places around the U.S. (or the world depending on how you read the question).

In order to strengthen a question that involves cause and effect, you will want to consider the possibility of blocking an alternate cause. In this case we are saying the cause is the "unnecessary procedures" so we want to block the things that would make these procedures necessary - like variations in the age of the population, the health of the people, the quality of the water, even the ability of the people to pay for the procedures.

Answer Choice B does this. It says, "The variation is unrelated to factors (other than the surgical procedures themselves) that influence the incidence of diseases for which surgery might be considered." So this blocks the idea that the cause of varying rates of procedures would be any of the factors (age, health, toxins) etc. mentioned above. So we strengthen one cause by blocking another.

Does that help you to think of approaching questions that feature a cause and an effect?

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