Is the standard deviation of A=0? 1) The minimum value of

Question

Is the standard deviation of A=0?
1) The minimum value of the elements in set A is 5
2) The set A has 20 elements

The OA is not E

KillerSquirrel · Answer

the answer is (E)

statement 1

can be:

set (5,5,5)

SD = 0

or

set (5,6,7)

insufficient

statement 2

no info on the elements in the set so:

insufficient

statement 1&2

can be:

set (5,5,5 ..... 5,5)

SD = 0

or

set (5,6,7,8,9 ..... )

insufficient

:-D

sumande · Answer

Not E !!!

Can't see how ??!!

iamba · Answer

I choose B.

A set should have distinct elements. So SD can not be zero

Himalayan · Answer

A. if 5 is minimum, then there should be a maximum value which different from 5. therefore there is/are some more values other than 5. so should be A.

KillerSquirrel · Answer

Sorry Himalayan but I disagree, since: MIN(5,5,5) = 5 MAX(5,5,5) = 5

sumande · Answer

I agree with KillerSquirrel. 
The question does not specify that the minimum and maximum values are different. We cannot assume that they are different! They may be the same!

Himalayan · Answer

yah, I know. I was just using a logic cuz msrinath said E is not OA. 8-)

sumande · Answer

What then is the OA? And, most importantly, the OE if OA is not E.

vshaunak@gmail.com · Answer

Can't imagine any OA other than 'E'

plaguerabbit · Answer

would the real GMAT really have questions like this?

If the OA really is not E, then this is more of a verbal question than a quant question lol... it's more of a play on words than it is a question testing mathematical concepts.

ywilfred · Answer

St1:
Nothing useful.

St2:
Even more useless than St1.

Using both:
Nothing useful really comes out.

E.

ian7777 · Answer

No. This is not a GMAT question, if the answer's not E.

vshaunak@gmail.com · Answer

Please post the OE, if you have it.

msrinath · Answer

This is a standard practice for GMAT 700+ questions, hiding information in plain sight. The hidden information here is that "A" is a set. As per the definition of sets, all the elements of a set are unique.
  

Now having this information in hand, lets start analysing the given statements

1] minimum value of elements in set A is 5.
=> Set could be {5} or {5,6 ...}
In first case SD=0   
In second case SD#0 since the numbers are different. So not sufficient

2] set A has 20 elements => A is a set AND it has more than 1 elements so it has 20 different elements and hence the SD cannot be 0. A positive "YES" to the asked question.

Choice B

OA is B

ishcabibble · Answer

Is that definition actually given in any of the review books? The only book I have on hand at the moment is the OG Quantitative Review, which says, "In mathematics a set is a collection of numbers or other objects". It says nothing about all elements being unique. I'll be sure to check out my myriad of other books at home tonight to see if that definition is given anywhere. If not, then that is a horribly unfair GMAT question!

vshaunak@gmail.com · Answer

I have never read that the set contains unique elements. 

The OG11 says - A set is a collection of numbers or objects. This doesn't mean that the numbers can't be same.

Can you please give some other authentic reference, which says the set consists of unique elements.

I wanna clarify it so that I can face the questions without doubt in mind.

Is the standard deviation of A=0? 1) The minimum value of

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