Sums of Discrete Random Variables
1. [Exercise 5.2.2] Let
,
, ...,
denote the outcomes when rolling
n
fair dice. Let
+
... +
equal the sum of these
n
rolls. Use animation to plot probability histograms for the distribution of
.
Solution
2. [Exercise 5.5.11] Let
,
, ...,
denote the outcomes when rolling
n
fair
m
-sided dice. Let
+
... +
equal the sum of these
n
rolls. Use animation to plot probability histograms for the distribution of
. Superimpose an approximating normal p.d.f.
Solution
3. [Exercise 5.2.4 and Exercise 5.2.17 of Hogg/Tanis] The power of the probability-generating function (factorial moment-generating function) for determining a p.d.f. can be illustrated with a very simple problem. Let
X
equal the number of times that an
n
-sided die must be rolled to observe each face at least once. The probability-generating function of
X
, as a function of
t
, is
. A CAS can expand
h
=
h
(
t
) and list the respective probabilities,
P
(
), the coefficients of
i
n the expansion.