IMO C

Standard deviation shows how much variation there is from the "average" (mean).

1. A low standard deviation indicates that the data points tend to be very close to the mean,
2. A high standard deviation indicates that the data are spread out over a large range of values.

you need both information to know complete list of integer sets.

IMO C

Stem

T={t1,t2,30,40,50} S={s1,s2,30,40,50}
Mean=40 Mean = 40

Statement one

S={s1,25,30,40,50}, Since we have mean, we can find s1. Therefore we have full set of S but no info about T.
Clearly Insuff

Statement two

T={t1,45,30,40,50}, Since we have mean, we can find t1. Therefore we have full set of T but no info about S.
Clearly Insuff

Combined
We have full set of S and full set of T and their means
variance formula is root(x-mean)^2/n-1

So we can find it
Suff

Hence C

eaakbari wrote:IMO C

My 2 cents here:

Set s :{ 30,40,50 , X, Y}

Since the avg is 40---then the total sum of 5 integers will be 200.

Set S : {200+X+Y}

For Set T :{200 +X+Y}

Now according to st 1 we can have { 30 ,40, 50, 25,55}

Still we are not sure of Set T. So st 1 alone is insufficient!!

Using st 2 alone wont help much as set T gives {30,40,50,45,35}

Combining both the sts 1 & 2 set 2 has closer standard deviation than set S.