Determine whether the following are valid probability models or not. Type "VALID" if it is valid, or type "INVALID" if it is not.
(a)
Event
e1, e2, e3, e4
Probability
0.2, 0.2, 0, 0.6
Answer:
(b)
Event
e1, e2, e3, e4
Probability
0.2, 0.2, −0.3, 0.9
Answer: