GMATPrerp DS

4meonly wrote:

OA is A


I marked correct answer using plug-ins, however, I need more scientific approach.

(1)
we have either set of odd or even nubers.
By testing
1-3-5-7-9 I got average=median
1-3-5-7 I got average=median
The same was with even numbers. I suppose that the same will be is I take not integers with difference equal to 2.
SUFF

(2)
Means that the range is even, so 1st and the last numbers both are either odd or even. But we dont know anything about other numbers in the set - they can be odd, even and not integers.
INSUFF

Anybody with more strong reasoning?

Statement 1)

Evenly spaced consecutive numbers.

Mean and Median is same for any consecutive numbers set. SUF

Statement 2)

Even range gives us no information.

2(n-1) = 2n - 2

So first term is 2 and the nth term is 2n but we have no idea whats going in between

2 5 6 where n=3 and 2n=6

2 3 6 where n=3 and 2n=6

logitech wrote: Statement 2)
Even range gives us no information.
2(n-1) = 2n - 2
So first term is 2 and the nth term is 2n

thanx
i overlooked this

logitech wrote:

4meonly wrote:

OA is A


I marked correct answer using plug-ins, however, I need more scientific approach.

(1)
we have either set of odd or even nubers.
By testing
1-3-5-7-9 I got average=median
1-3-5-7 I got average=median
The same was with even numbers. I suppose that the same will be is I take not integers with difference equal to 2.
SUFF

(2)
Means that the range is even, so 1st and the last numbers both are either odd or even. But we dont know anything about other numbers in the set - they can be odd, even and not integers.
INSUFF

Anybody with more strong reasoning?

Statement 1)

Evenly spaced consecutive numbers.

Mean and Median is same for any consecutive numbers set. SUF

Statement 2)

Even range gives us no information.

2(n-1) = 2n - 2

So first term is 2 and the nth term is 2n but we have no idea whats going in between

2 5 6 where n=3 and 2n=6

2 3 6 where n=3 and 2n=6

logitech,
I also overlooked this part. Thanks for the expln though.....

Bro,

Mean and median 'are'. We have to keep a check on this.

I think we can generalize and say mean and median are the same for an a set whose common difference between successive(after arranging them in ascending) elements are the same

Consecutive numbers
Consecutive even integers
Consecutive odd integers

(OR)

0 100 200 300 400 COMMON DIFFERENCE - 100

I am thinking if we can say for an arithmetic progression(where the common difference is the same) the mean is the median. Feedback welcome and someone correct me if this generalization will not work!

Thus stmt I is sufficient


Stmt II

Picking numbers is the safest route to disprove this

0 2 4 6 8 Range 2(n-1) and mean = median

0 1 3 5 8 Range = 2(n-1) and mean not equal to median

INSUFF

A)

AH

for statement 2, i pluggd in successive values for n and the range always moved by 2 so i thought B was sufficient too. fell for the trap.