What is the standard deviation of the terms in set N? (1) Every prime

What is the source? The wording is too imprecise for the question to be interpreted unambiguously, and it is using the term 'range', which has a specific meaning in Statistics, to mean something other than 'range'. I'm not sure what "range" even means here, because often when we say "range" in phrases similar to that used in this question, we mean that the endpoints are automatically included. If you say "salaries at Company X range from $20,000 to $100,000", that means one salary definitely is $20,000, and another definitely is $100,000. Does Statement 2 here mean to suggest that 20 and 50 are both in the set? I can't tell.

But as I'd interpret the wording, we know almost nothing about N even using both Statements, besides the fact that its elements lie between 20 and 50. Our set could be

{23, 27}

say, because "every prime number in a specific range (the range from 21 to 25, say) appears exactly once", and all of the terms are between 20 and 50. Or the set could be

{23, 49}

for the same reason, and these two sets clearly have different standard deviations. So E is the answer, as I read the question.

target what is SD of set N
#1
Every prime number in a specific range appears exactly once in set N.
no info about set range of numbers insufficient
#2
All terms in set N range between 20 and 50.
no info whether all the numbers between 20 and 50 are there or is it a set a specific numbers ( odd, even , prime etc )
insufficient
from 1 &2
we cannot conclusively say that the set N has only prime numbers or it has prime numbers + other numbers from 21 to 49 or numbers in any other order

insufficient
option E is correct ..

What if the set also includes composite numbers?

Statement (1) Every prime number in a specific range appears exactly once in set N.
We do not know the elements of the set; Hence, Not sufficient

Statement (2) All terms in set N range between 20 and 50.
We do not know the elements of the set; Hence, Not sufficient

Combined :
Language of the statement 1 is not very clear to me
Assuming it says set consists of elements which are prime number between a specific range and there are no other element. Statement 2 gives the specific range. so we know the elements of the set and hence the SD-Sufficient

If statement one imply there are other elements in the set along with prime numbers between specific range our answer when we combine two statements will remain Not sufficient

I pick C.

What is the standard deviation of the terms in set N?

SD of set N.

(1) Every prime number in a specific range appears exactly once in set N.
Clearly not sufficient. We have unlimited prime number. So we don't know regarding the number of terms in the list.
Not sufficient.

(2) All terms in set N range between 20 and 50.
Let us take a example , { 30,30,30,30,30}
30 lies in the range of 20 to 50.
SD of the above set = 0

Let us take another example within the same range { 32,34,36,38,40}
SD of set approx. =2.4

Clearly conflicting answers
Not sufficient.

Combining both statements.
Prime number comes exactly once and lies in the range of 20 to 50.
List of prime numbers in the given range {23,29,31,37,41,43,47}
Well now we have a fixed set of elements
We have some fixed value of SD.
Sufficient.

IMO C

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