If the first term

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sreak1089: Master | Next Rank: 500 Posts; Posts: 379; Joined: Wed Jun 03, 2009 3:05 amFollowed by: 1 member; Thanked: 19 times; GMAT Score:690

by sreak1089 » Thu Aug 13, 2009 4:24 am

Hi Scoobydooby, stmt # 1 says range is zero => first and last terms are equal to 3. Now the middle term has to be any number between 3 & 3 and only possibility is to be 3 itself. Hence sufficient. But, biggest doubt I have is that the problem stem talks about sets and as far as I know, a set should contain distinct elements. Hence, how can three terms, all be equal to 3?????

scoobydooby wrote:D seems better than B as i reread the stimulus.

it says the first term is 3. asks for the 3rd term. the use of "1st" and "3rd" seems to be hinting that the set is ordered.

if {3, y, z} is in increasing order, from stment 1, z must be 3
if {3, y, z} is in decreasing order, from stment 1, z must be 3

stment 1 is sufficient in itself.

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scoobydooby: Legendary Member; Posts: 1035; Joined: Wed Aug 27, 2008 10:56 pmFollowed by: 1 member; Thanked: 104 times

by scoobydooby » Thu Aug 13, 2009 4:37 am

hey sreak1089,

the question says "data set". i guess it just implies a collection of numbers. dont think we have to use conventional set theory definitions. the problem would have defined it if we had to use it.
i may be wrong, we shall get to know how to interpret "set" once the OA is out

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Ian Stewart: GMAT Instructor; Posts: 2623; Joined: Mon Jun 02, 2008 3:17 amFollowed by: 355 members; Location: Montreal; Thanked: 1090 times; GMAT Score:780

Re: If the first term

by Ian Stewart » Sat Aug 15, 2009 5:25 pm

madhur_ahuja wrote:{x,y,z}

If the first term in the data set above is 3, what is the third term?
(1) The range of this data set is 0.
(2) The standard deviation of this data set is 0.

Just to clarify a few points:

-sets are not ordered, so it makes no mathematical sense to talk about the 'first term' or the 'third term' in a set. So the question above is not well-designed - where is it from?

-in statistics, data sets can contain repeated elements. {3, 3, 3} is a perfectly acceptable data set. Most GMAT stats questions are about data sets. The concept of the 'mode', for example, wouldn't make any sense if sets never contained repeated elements;

-if the range of a data set is zero, or if the standard deviation of a data set is zero, all of the elements in the set are equal.

For online GMAT math tutoring, or to buy my higher-level Quant books and problem sets, contact me at ianstewartgmat at gmail.com

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