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# Student: The majority of the 50 students in my class

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Manager
Joined: 20 Nov 2010
Posts: 228
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Kudos [?]: 5 [0], given: 38

Student: The majority of the 50 students in my class [#permalink]  10 Sep 2012, 22:38
00:00

Difficulty:

5% (low)

Question Stats:

87% (01:36) correct 12% (00:23) wrong based on 16 sessions
Student: The majority of the 50 students in my class answered at least 80% of the questions correctly on last year’s Algebra I exam. If these final exam scores do accurately measure the level of a student’s level of understanding, Marc must have learned less about Algebra last year than most other students in the class because he answered only 75% of the questions correctly on the Algebra I exam.
Which of the following, if true, most seriously, weakens the student’s argument?

A. Seven students answered less than 75% correctly on the exam.
B. Marc is one of four students in the class who did not take an introductory level Algebra course before Algebra I.

[Reveal] Spoiler:
I marked A but the OA is B. Still not convinced. Please help!
[Reveal] Spoiler: OA

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CR notes
http://gmatclub.com/forum/massive-collection-of-verbal-questions-sc-rc-and-cr-106195.html#p832142
http://gmatclub.com/forum/1001-ds-questions-file-106193.html#p832133
http://gmatclub.com/forum/gmat-prep-critical-reasoning-collection-106783.html
http://gmatclub.com/forum/how-to-get-6-0-awa-my-guide-64327.html
http://gmatclub.com/forum/how-to-get-6-0-awa-my-guide-64327.html?hilit=chineseburned

Senior Manager
Joined: 15 Jun 2010
Posts: 363
Schools: IE'14, ISB'14, Kellogg'15
WE 1: 7 Yrs in Automobile (Commercial Vehicle industry)
Followers: 5

Kudos [?]: 106 [0], given: 50

Re: weaken question - powerscore - numbers [#permalink]  10 Sep 2012, 22:49
catfreak wrote:
Student: The majority of the 50 students in my class answered at least 80% of the questions correctly on last year’s Algebra I exam. If these final exam scores do accurately measure the level of a student’s level of understanding, Marc must have learned less about Algebra last year than most other students in the class because he answered only 75% of the questions correctly on the Algebra I exam.
Which of the following, if true, most seriously, weakens the student’s argument?

A. Seven students answered less than 75% correctly on the exam.
B. Marc is one of four students in the class who did not take an introductory level Algebra course before Algebra I.

[Reveal] Spoiler:
I marked A but the OA is B. Still not convinced. Please help!

B is correct. It shows that the comparison is not parallel. It was a apple vs orange comparison. Marc's background was not similar to most of the students.

Ans choice A is incorrect: It does not hurt the conclusion. In-fact it is consistent with the conclusion. majority of 50 means greater than 25. So if let say 30 students scored more than 80% & 7 scored less than 75%, it is not hurting the conclusion.
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Kudos [?]: 561 [1] , given: 3

Re: weaken question - powerscore - numbers [#permalink]  11 Sep 2012, 08:20
1
KUDOS
The key phrase in the stem is the following: Marc must have learned less about Algebra last year than most other students.

The question is comparing how much algebra Marc and other students *learned* during the year. If Marc knew nothing about algebra at the start of the year, and half his class were already experts before the year started, then Marc may have learned a lot more than everyone else during the year and still gotten a lower score than the expert students on the exam. That's what answer B is getting at.
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Re: weaken question - powerscore - numbers   [#permalink] 11 Sep 2012, 08:20
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# Student: The majority of the 50 students in my class

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