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Standard deviation .. Conceptual and advanced one [#permalink]
12 Jan 2010, 03:16

00:00

A

B

C

D

E

Difficulty:

(N/A)

Question Stats:

8% (00:00) correct
92% (00:39) wrong based on 20 sessions

Both the ranges of 2 lists are from 1 to 100, whose deviation is greater? 1) List 1 has three 100 and two 50; List 2 has two 100 and three 50. 2) The averages are the same.

One alone can not help : We can have list of numbers in any fashion as only range has to be within limit of 100 . not sufficent

Obviously two alone is not adequate to answer the question a well . If mean are same , does not mean anything for SD unless you know the variation of its elemnt from the mean. not sufficient.

Is it possible to answer if one and two are together ? Answers with explanations only please.

Re: Standard deviation .. Conceptual and advanced one [#permalink]
12 Jan 2010, 04:38

Statement 2 is insufficient.

I do not understand Statement 1 though: Does it give complete enumeration of numbers in lists? OR it only mentions some numbers that are in lists? (albeit here could be other numbers we know nothing about)

Re: Standard deviation .. Conceptual and advanced one [#permalink]
13 Jan 2010, 02:36

Hi, Both the statements are individually as well as together are insufficient to answer the question.

For Standard Deviation we need to know the mean and the numbers in the distribution. Here, without the numbers in distribution we are unable to determine the mean and deviation from the mean.

Re: Standard deviation .. Conceptual and advanced one [#permalink]
13 Jan 2010, 06:45

I would rather say, to know the SD of a set/list, we need to know the mean, the elements and the "number of elements" specifically as well. We only have the range information, which does not help us know anything about the total number of elements in each list given. The occurrence of a specific element in a list can become irrelevant depending on the number of elements.

Re: Standard deviation .. Conceptual and advanced one [#permalink]
12 Feb 2010, 23:30

GMATMadeeasy wrote:

Both the ranges of 2 lists are from 1 to 100, whose deviation is greater? 1) List 1 has three 100 and two 50; List 2 has two 100 and three 50. 2) The averages are the same.

One alone can not help : We can have list of numbers in any fashion as only range has to be within limit of 100 . not sufficent

Obviously two alone is not adequate to answer the question a well . If mean are same , does not mean anything for SD unless you know the variation of its elemnt from the mean. not sufficient.

Is it possible to answer if one and two are together ? Answers with explanations only please.

Statement 1 & 2 alone cannot solve. To find SD we need to know how far each element is from mean. Even taking both together, if average is same for both sets we do not know the difference of each element from mean henceforth cannot solve this problem with both statements even so E.

Re: Standard deviation .. Conceptual and advanced one [#permalink]
06 Oct 2010, 10:30

Expert's post

GMATMadeeasy wrote:

Both the ranges of 2 lists are from 1 to 100, whose deviation is greater? 1) List 1 has three 100 and two 50; List 2 has two 100 and three 50. 2) The averages are the same.

One alone can not help : We can have list of numbers in any fashion as only range has to be within limit of 100 . not sufficent

Obviously two alone is not adequate to answer the question a well . If mean are same , does not mean anything for SD unless you know the variation of its elemnt from the mean. not sufficient.

Is it possible to answer if one and two are together ? Answers with explanations only please.

The wording of this question is terrible - where is it from? The 'range' of a set is a single number, the difference of the largest and smallest elements. We don't say that 'the range is from 1 to 100'; that's misusing terminology. The term 'deviation' in statistics is also not interchangeable with 'standard deviation'; the 'deviation' of an element x is the difference between x and the mean. It's meaningless to talk about the deviation of a list. I'm sure the question means to discuss standard deviation instead. If so, the answer is certainly E; we have almost no information about how the elements in the lists are distributed. _________________

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