Question

If X denotes the number on the upper face of a cubical die when it is thrown, find the mean of X.

Answer 1

A cubical die can show 1, 2, 3, 4, 5 or 6 on its face.

xi	pi	pixi
1	$\frac{1}{6}$	$\frac{1}{6}$
2	$\frac{1}{6}$	$\frac{2}{6}$
3	$\frac{1}{6}$	$\frac{3}{6}$
4	$\frac{1}{6}$	$\frac{4}{6}$
5	$\frac{1}{6}$	$\frac{5}{6}$
6	$\frac{1}{6}$	$\frac{6}{6}$

Mean = ${\sum }_{}^{}$p_ix_i = $\frac{1}{6}+\frac{2}{6}+\frac{3}{6}+\frac{4}{6}+\frac{5}{6}+\frac{6}{6}=\frac{21}{6}=3.5$