Assignment 11
There are three makes of computers in a lab, Dell, IBM and Macintosh. The lab manager assigns
students to computers as they enter by the throw of a fair 8-sided die.
\(\bullet\) If a 1 appears the student is sent to the Dell,
\(\bullet\) If a 2,3,or 4 appears, to the IBM,
\(\bullet\) If a 5,6,7 or 8 appears, to the Macintosh.
Because of the way that the systems were installed the students have the
following conditional probabilities of being able to logon.
\(\bullet\) Dell: 1/2,
\(\bullet\) IBM 1/3.
\(\bullet\) Macintosh 2/3.
\(\bullet\) Otherwise, the logon fails.
a. Here is a tree for this situation. Enter the probabilities, the conditional probabilities and
the joint probabilities in the appropriate boxes.
Logon succeeds
Logon fails
Dell
Logon succeeds
IBM
Logon fails
Mac
Logon succeeds
Logon fails
b. What is the probability that someone was assigned to the Dell and was able to logon?
c. What is the probability that someone who was able to logon had been assigned to the
Macintosh?
