Tell me more ×
Mathematics Stack Exchange is a question and answer site for people studying math at any level and professionals in related fields. It's 100% free, no registration required.

We roll two fair dice, a blue and a red one, independently of each other. Let X be the number obtained on the blue die minus the number obtained on the red die. Draw a histogram for its probability function and a graph for its distribution function.

share|improve this question
2  
Homework? Where are you having difficulties? – Henry Apr 18 '12 at 13:36

closed as too localized by BenjaLim, Michael Greinecker, William, Sasha, wentaway Sep 7 '12 at 12:43

This question is unlikely to help any future visitors; it is only relevant to a small geographic area, a specific moment in time, or an extraordinarily narrow situation that is not generally applicable to the worldwide audience of the internet. For help making this question more broadly applicable, see the FAQ.

1 Answer

Hint: The sample space for $X=\color{blue}{B}-\color{red}{R}$ decomposes as the cartesian product $\{(\color{blue}{B},\color{red}{R})\}=\{1,2,\dots,6\}^2$ in terms of the values obtained on each colored die (red & blue respectively). $$ \begin{array}{rrrrrrr} X && \color{red}{1} & \color{red}{2} & \color{red}{3} & \color{red}{4} & \color{red}{5} & \color{red}{6} \\\\ \color{blue}{1} && 0 & -1 & -2 & -3 & -4 & -5 \\ \color{blue}{2} && 1 & 0 & -1 & -2 & -3 & -4 \\ \color{blue}{3} && 2 & 1 & 0 & -1 & -2 & -3 \\ \color{blue}{4} && 3 & 2 & 1 & 0 & -1 & -2 \\ \color{blue}{5} && 4 & 3 & 2 & 1 & 0 & -1 \\ \color{blue}{6} && 5 & 4 & 3 & 2 & 1 & 0 \end{array} $$ Can you deduce the histogram from this and then normalize that to get the probability density function?

share|improve this answer

Not the answer you're looking for? Browse other questions tagged or ask your own question.