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Set T consists of a certain number of even integers divisible by 3. Is standard deviation of T positive?

1:All elements of set T are positive 2:The range of set T is 0

B.

1: T could have diffierent or same +ve integers. nsf... 2: T has same +ve integers. so range = 0. Hence T has zero (0) or non-positive SD. suff.
_________________

Set T consists of a certain number of even integers divisible by 3. Is standard deviation of T positive?

1:All elements of set T are positive 2:The range of set T is 0

2)solves the issue since 0 = range means all equal values !!!SD=0 which is neither +ve nor -ve 1)All elements are +ve means the deviation is always +ve irrespective of individual values!!!

IMO D

one doubt is that I thought SD is always +ve since its RMS value of deviations !!!Please clearify and is the AREA of the graph !!
_________________

I would bet all my money to say that SD is always +ive

SD=sqrt(sum((xi-mean)^2))

How can be it -ive?

What is the source of the problem?

Cheers
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This is a wrong question. SD is always positive. The basic idea of the standard deviation is that you're measuring variations around the mean value. Some of those values will be below the mean, some above and sometimes you'll have some that are equal to the mean. In other words some of the differences between the individual measurements will be positive (more than the mean), some will be negative (below the mean) and some will be zero (directly equal to the mean). Now just adding these differences up is dangerous because the positive and negative values will cancel each other out. For example, to take an incredibly simplistic case, if you've got a sample of two values, one of 9 and one of 11, the mean is equal to 10. The differences are -1 and +1, adding these together gives us a total variation of 0. But we know that there's not zero variation around that mean value!

So, to get round this problem each of the variations around the mean is squared. When you square a negative value you get a positive value.

I am great... and you can sue my Leo sun for that statement

i) Find the mean of the set of numbers ii) Find the difference between each of the numbers and the mean iii) Square the differences and take the mean of the differences iv) Take the positive square root of this value

_________________

"You have to find it. No one else can find it for you." - Bjorn Borg

if I consider the problem again, taking into account that SD can be 0 or greater than 0:

1 Suff. because all elements are greater than 0. The solution is "yes"

2 Suff. because the range equals 0 means that the maximum number and the minimum are equal. Therefore, SD = 0. Answer "no"

However, I get 2 different answers which I think is not possible on a real GMAT exam, isn't it?
_________________

mates, please visit my profile and leave comments http://gmatclub.com/forum/johnlewis1980-s-profile-feedback-is-more-than-welcome-80538.html

I'm not linked to GMAT questions anymore, so, if you need something, please PM me

I'm already focused on my application package

My experience in my second attempt http://gmatclub.com/forum/p544312#p544312 My experience in my third attempt http://gmatclub.com/forum/630-q-47-v-28-engineer-non-native-speaker-my-experience-78215.html#p588275