Which of the Following Statements Are True If $X _ { 1 } , X _ { 2 } , \cdots \cdots , X _ { n }$

Multiple Choice

Which of the following statements are true if $X _ { 1 } , X _ { 2 } , \cdots \cdots , X _ { n }$ is a random sample from a distribution with mean $\mu \text { and variance } \sigma ^ { 2 }$ ?

A) $S ^ { 2 } = \sum ( X - \bar { X } ) ^ { 2 } / ( n + 2 ) \text { is an unbiased estimator of } \sigma ^ { 2 }$
B) $S ^ { 2 } = \sum ( X - \bar { X } ) ^ { 2 } / ( n + 1 ) \text { is an unbiased estimator of } \sigma ^ { 2 }$
C) $S ^ { 2 } = \sum ( X - \bar { X } ) ^ { 2 } / n \text { is an unbiased estimator of } \sigma ^ { 2 }$
D) $S ^ { 2 } = \sum ( X - \bar { X } ) ^ { 2 } / ( n - 1 ) \text { is an unbiased estimator of } σ^ { 2 }$

E) All of the above statements are true provided that the sample size n > 30.