Which of the Following Statements Are True?
A) Methods for Comparing

Which of the following statements are true?

A) Methods for comparing two population variances (or standard deviations) are occasionally needed, though such problems arise much less frequently than those involving means or proportions.
B) If $X _ { 1 } \text { and } X _ { 2 }$
Are independent chi-squared random variables with $v _ { 1 } \text { and } v _ { 2 }$
Degrees of freedom, respectively, divided by their respective degrees of freedom can be shown to have an F distribution.
C) The density curve of an F distribution is positively skewed (skewed to the right) .
D) All of the above statements are true.
E) None of the above statements are true.