Which of the Following Formulae Is Used in the Computation $\sqrt { \frac { ( X - M ) ^ { 2 } } { N } }$

Multiple Choice

Which of the following formulae is used in the computation of the confidence interval for the mean?

A) $\sqrt { \frac { ( X - M ) ^ { 2 } } { N } }$
B) $\frac { X - M } { \sigma }$
C) $M \pm \frac { \left( t _ { .05 } \right) ( S ) } { \sqrt { N } }$
D) $\frac { \sum ( X - M ) ^ { 2 } } { N }$