Data Sufficiency

Economist GMAT

Group \(X\) has \(6\) students \(3\) boys who are each \(j\) years old, and \(3\) girls who are each \(k\) years old. Group \(Y\) has \(4\) students, \(1\) boy who is \(j\) years old and \(3\) girls who are each \(k\) years old. What is the variance of the ages in group \(Y\)?

1) The standard deviation of \(X\) is \(0\).
2) \(j=k\).

OA D

Statement 1
We have that standard deviation \(=0\) this will happen only when all the terms in the set are the same.
Hence \(j=k\), Variance \(= 0\).
Sufficient

Statement 2
We have the same \(j=k \Rightarrow\) Variance \(=0\).
Sufficient

Hence, __D__ is the correct option.