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VP
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Question Stats:
50% (02:35) correct
50% (00:35) wrong based on 0 sessions
The following table shows results of a quality inspection of a lot of 15 mirrors. Defects Frequency _0 ________ 6 _1 ________ 1 _2 ________ 4 _3 ________3 _4 ________1 The difference between the median defects and the average defects in the sample checked is between: (A) -1 and 0 (B) 0 and 0.5 (C) 0.5 and 1 (D) 1 and 1.5 (E) 1.5 and 2 Source: GMAT Club Tests - hardest GMAT questions
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Director
Joined: 13 Dec 2006
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B = 0 and 0.5
In the sample of 15 numbers, median will be (7th + 8th)/2, in this case 7th number is 1 and 8th number is 2 so median = 1.5
Average of the number is addition of all the numbers of defects divided by 15 = 3/5,
so Median - avg = 9/10, which lies between 0 and 0.5
Amar
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VP
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i think i cannot read the table. where are the lots of 15 mirrors. how are they represented in the table?
thanks
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Manager
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Amardeep Sharma wrote: B = 0 and 0.5
In the sample of 15 numbers, median will be (7th + 8th)/2, in this case 7th number is 1 and 8th number is 2 so median = 1.5
Average of the number is addition of all the numbers of defects divided by 15 = 3/5,
so Median - avg = 9/10, which lies between 0 and 0.5
Amar
I did it the same way, but, and Im sure Im being a moron, why if there are an odd number of mirrors do we need to average two items - surely the 8th mirror is the median?
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Director
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Yep, you are right and I am wrong... thnx for correcting me.... 
I dont know how I made that mistake, well as you got median as 2, rest will follow the same procedure
thanx once again
Amar
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Manager
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Ravshonbek wrote: The following table shows results of a quality inspection of a lot of 15 mirrors.
Defects Frequency
_0________ 6
_1________ 1
_2________ 4
_3 ________3
_4 ________1
The difference between the median defects and the average defects in the sample checked is between:
0
0 and 0.5
0.5 and 1
1 and 1.5
1.5 and 2
I am missing something here:
Median - 2
Mean - {0(6) + 1(1) + 2 (4) + 3 (3) + 4 (1)}/15 = 1.47
Difference b/c Median & Avg: 2 - 1.47 = 0.53
What is the OA?
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Manager
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GMATBLACKBELT wrote: yogachgolf wrote: Ravshonbek wrote: The following table shows results of a quality inspection of a lot of 15 mirrors.
Defects Frequency
_0________ 6
_1________ 1
_2________ 4
_3 ________3
_4 ________1
The difference between the median defects and the average defects in the sample checked is between:
0
0 and 0.5
0.5 and 1
1 and 1.5
1.5 and 2 I am missing something here: Median - 2 Mean - {0(6) + 1(1) + 2 (4) + 3 (3) + 4 (1)}/15 = 1.47 Difference b/c Median & Avg: 2 - 1.47 = 0.53 What is the OA? I get the same I too get the same, 0.53. We are not concerned with the sample size, but, only with the number of defects in the given sample.
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Manager
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Difference between median & mean is 0.53, Ans. C)
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Manager
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A similar problem exists in GMAT club challenge 24 (question 26). Check out its explanation.
rakesh22 wrote: GMATBLACKBELT wrote: yogachgolf wrote: Ravshonbek wrote: The following table shows results of a quality inspection of a lot of 15 mirrors.
Defects Frequency
_0________ 6
_1________ 1
_2________ 4
_3 ________3
_4 ________1
The difference between the median defects and the average defects in the sample checked is between:
0
0 and 0.5
0.5 and 1
1 and 1.5
1.5 and 2 I am missing something here: Median - 2 Mean - {0(6) + 1(1) + 2 (4) + 3 (3) + 4 (1)}/15 = 1.47 Difference b/c Median & Avg: 2 - 1.47 = 0.53 What is the OA? I get the same I too get the same, 0.53. We are not concerned with the sample size, but, only with the number of defects in the given sample. |
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Intern
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i too get the answer as C.....please post the OA....
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VP
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OA is C, thanks a million
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Manager
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Ravshonbek wrote: The following table shows results of a quality inspection of a lot of 15 mirrors.
Defects Frequency
_0________ 6
_1________ 1
_2________ 4
_3 ________3
_4 ________1
The difference between the median defects and the average defects in the sample checked is between:
0
0 and 0.5
0.5 and 1
1 and 1.5
1.5 and 2 the arrangement would be as under 0 0 0 0 0 0 1 2 2 2 2 3 3 3 4 here the median is 2The mean is 1.47 (22/15) the answer is 2-1.47 = 0.53 (C)
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Intern
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15 mirrors, but with a total number of 22 as defective?
I don't understand this:(
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Foiled by poor reasoning 
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cnrnld wrote: 15 mirrors, but with a total number of 22 as defective?
I don't understand this:( It implies that the company is measuring more than one type of defect.
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GaryDunn wrote: cnrnld wrote: 15 mirrors, but with a total number of 22 as defective?
I don't understand this:( It implies that the company is measuring more than one type of defect. Its 22 defects in 15 lots of 15 mirrors each. I Got C.
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Intern
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GMATBLACKBELT wrote: yogachgolf wrote: Ravshonbek wrote: The following table shows results of a quality inspection of a lot of 15 mirrors.
Defects Frequency
_0________ 6
_1________ 1
_2________ 4
_3 ________3
_4 ________1
The difference between the median defects and the average defects in the sample checked is between:
0
0 and 0.5
0.5 and 1
1 and 1.5
1.5 and 2 I am missing something here: Median - 2 Mean - {0(6) + 1(1) + 2 (4) + 3 (3) + 4 (1)}/15 = 1.47 Difference b/c Median & Avg: 2 - 1.47 = 0.53 What is the OA? I get the same I also got the same thing.
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Intern
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Amardeep Sharma wrote: B = 0 and 0.5
In the sample of 15 numbers, median will be (7th + 8th)/2, in this case 7th number is 1 and 8th number is 2 so median = 1.5
Average of the number is addition of all the numbers of defects divided by 15 = 3/5,
so Median - avg = 9/10, which lies between 0 and 0.5
Amar Whoah there tiger. Median of 15 terms is the 8th term, not the average of 7th and 8th. Median is 2. Mean of any set which consists of n odd integers is Quotient (n/2) + 1 = 15/2 + 1 = 8th term Mean of any set which consists of n even integers is the average of the "n"th and "n+1" term For any arithmetic progression, Mean = Median = Average = Average of first and last term Back to the problem.............. Average = 22/15, which is a little bit less than 1.5 (Why ? Because 1.5 x 1.5 = 225. Knowledge of squares comes in handy here. The GMAT never asks you to do busy work. Always remember that !!! ) Difference = 2 - (a term that is a little bit less than 1.5) = A term that is a little bit more than 0.5 Answer - c
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