# Math Help - [SOLVED] Mean and Variance Question...

1. ## [SOLVED] Mean and Variance Question...

Question:
The random variable $T$ has the probability distribution given in the following table.

Attempt:

$E(T) = 4 , Var(T) = 19.6$

Where did I go wrong?

2. your definition of variance is wrong it's supposed to be:

$VAR(t) = \sum\limits_i {\left( {t_i - < t > } \right)^2 p(t_i )}$

or equivalently:

$
VAR(x) = \sum\limits_i {t_i ^2 p(t_i )} - \left[ {E(T)} \right]^2 = 19.6 - 16 = 3.6
$