sud21 wrote:A sequence: 2, 4, 6, ...22. Sequence M contains eight numbers, which are elements of the former sequence. What is the standard deviation of M?
1) Two sequences have the same average value.
2) M does contain 22

The original sequence contains 11 elements. To find the standard deviation of a new set, we need to know which elements are in the new sequence.

The original sequence is an arithmetic sequence, so its median is equal to its mean. This will be the 6th term, or 12.

The new sequence, however, is not guaranteed to be arithmetic!

Statement 1 alone is not sufficient. For example, we COULD have 2, 4, 6, 8, 16, 18, 20, 22 or we could have 2, 4, 6, 10, 14, 18, 20, 22 or 4, 6, 8, 10, 14, 16, 18, 20...

Statement 2 alone is not sufficient. We could have 2, 4, 6, 8, 16, 18, 20, 22 or 2, 4, 6, 10, 14, 18, 20, 22 or even the non-symmetrical 4, 6, 10, 12, 14, 18, 20, 22...

Even together the statements are not sufficient; we could still have 2, 4, 6, 8, 16, 18, 20, 22 or 2, 4, 6, 10, 14, 18, 20, 22.

Even after considering both the Statements 1 and 2, we get overall 2 sets i.e

(i) {2, 4, 6, 8, 16, 18, 20, 22}

OR

(ii) {2, 4, 6, 10, 14, 18, 20, 22}


Because of that the correct answer is E and not C...

Thank You.