Then nth moment of a continuous random variable X is defined by:
1
\(E\left( {{X^n}} \right) = \mathop \smallint \limits_0^\infty {x^n}{f_x}\left( x \right)dx\)
2
\(E\left( {{X^n}} \right) = \mathop \smallint \nolimits_{ - \infty }^0 {x^n}{f_x}\left( x \right)dx\)
3
\(E\left( {{X^n}} \right) = \mathop \smallint \limits_{ - \infty }^\infty {x^n}{f_x}\left( x \right)dx\)
4
\(E\left( {{X^n}} \right) = \mathop \smallint \limits_0^\infty {x^{n - 1}}{f_x}\left( x \right)dx\)