Question

Calculate the expected value E(X) of the given random variable X. X is the higher number when two dice are rolled, or the common number if doubles are rolled. (So, a roll of 4-3 would be given a value of 4 while a roll of 5-5 would be given a value of 5).

Answer 1

Answer:

4.4722

Step-by-step explanation:

The following table shows the 36 elements of the sample space of the experiment

$\left[\begin{array}{cccccccc}&1&2&3&4&5&6\\--&--&--&--&--&--&--\\1\;|&1&2&3&4&5&6\\2\;|&2&2&3&4&5&6\\3\;|&3&3&3&4&5&6\\4\;|&4&4&4&4&5&6\\5\;|&5&5&5&5&5&6\\6\;|&6&6&6&6&6&6\end{array}\right]$

From this table we can compute the probabilities :

P(X = 1) = 1/36

P(X = 2) = 3/36

P(X = 3) = 5/36

P(X = 4) = 7/36

P(X = 5) = 9/36

P(X = 6) = 11/36

So the expected value equals

1P(X=1)+2P(X=2)+3P(X=3)+4P(X=4)+5P(X=5)+6P(X=6) =

= 1/36 + 6/36 + 15/36 + 28/36 + 45/36 + 66/36 = 161/36 =  

4.4722