Answer:
a)
b)
Step-by-step explanation:
Given:
The lifetimes of the individual items are independent exponential random variables.
Mean = 200 hours.
Assume, Ti be the time between ( )st and the
failures. Then, the
are independent with
being exponential with rate
Therefore,
a)
The variance is given by,
Answer:
The questions and problem can be chosen in 1260 ways.
Step-by-step explanation:
Given that, a physics exam consists of 6 open-ended problem and 9 multiple choice questions.
The order of choosing does not matter.
So,we use combination to find ways.
The ways to choose 6 multiple choice from 9 is=
=84
The ways to 2 open-ended question from 6 is=
=15
Since pick 6 multiple choice out of 9 and 2 open-ended question out of 6 both are independent we have multiply both to find required ways.
Total number of ways is =(84×15)
=1260.