# probabilty mass function

• Apr 18th 2013, 07:26 AM
legakwa
probabilty mass function
For assessment
You roll two fair standard dice and record the num-
bers showing. Let T be the random variable \the sum of the two
numbers rolled" and D be the random variable \the absolute value of
the di erence between the two numbers rolled".
(a) Find the probability mass function of T.
(b) Find the expectation of T.

(c) Find the probability mass function of D.
(d) Find the expectation D
• Apr 18th 2013, 08:07 AM
Plato
Re: probabilty mass function
Quote:

Originally Posted by legakwa
For assessment
You roll two fair standard dice and record the num-
bers showing. Let T be the random variable \the sum of the two
numbers rolled" and D be the random variable \the absolute value of
the di erence between the two numbers rolled".
(a) Find the probability mass function of T.
(b) Find the expectation of T.

(c) Find the probability mass function of D.
(d) Find the expectation D

@legakwa, you must show work on this problem.
Look at this webpage. The coefficients tell us the number of ways a sum can happen. For example $4x^9$ tells us that the sum of nine occurs four ways out of thrifty-six pairs.

Now you work out the probability mass function of T.

For the second part: D can have values $0,1,\cdots,5$