There is a set of number, the mean is m, the standard

Question

There is a set of number, the mean is m, the standard deviation is R, if add a number x to this set, is x<=R?
1) x=m 
2) m<x<m+R

Dont know the answer, please explain.

walker · Answer

I guess E

Consider two possible sets:

first set: (-101,-100,-99): mean (m) is -100, standard deviation is about 1
second set: (99,100,101): mean (m) is 100, standard deviation is about 1

1. or 2.
for first set x will be -100 or between -100 and -99 that are lesser than 1
for second set x will be 100 or between 100 and 101 that are greater than 1

1&2 are incompatible.

jingy77 · Answer

am i wrong here or do the statement contradict each other?

1)x=m
2)x<m

elmagnifico · Answer

this one doesn't make sense to me. 
1 and 2 cannot have opposite assumptions!

tekno9000 · Answer

I presume statement A is true.

When a no. which is equal to mean is added to the set, the std dev. does not change.

I am lost with the second statement.

please correct me if I am wrong.

Value · Answer

Sorry Friends its r<=R not x<=R.

anirudhoswal · Answer

Maybe you could edit the original post also.
I did the whole thing before I read your correction.

Thanks

anirudhoswal · Answer

With r that x is larger than the mean. That means it is away from the center of the curve. So std. deviation must increase. (look at it like ( mean(x) - x(i) ) ^2 will add to the calcualtion of r). so r>R. So the info is SUFF to answer.
Thus, IMO: D

There is a set of number, the mean is m, the standard

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