Question 565349: The probabilities that the serviceability of a new laser printer will be rated very difficult, difficult, average, easy or very easy are 0.11, 0.16, 0.35, 0.28, 0.10 respectively. Find the probability that the serviceability of a new laser printer will be rated (i) difficult or very difficult. (ii) difficult, average or easy. and (iii) average or better.
Answer by Theo(13342)   (Show Source):
You can put this solution on YOUR website! probabilities for service ratings are:
very difficult .11
difficult .16
average .35
easy .28
very easy .10
presumably these ratings are independent of each other, i.e. a laser printer can be difficult to service or it can be easy to service but it can't be both at the same time.
this makes p(a or b) equal to p(a) + p(b)
if they were not independent of each other, then p(a or b) would be equal to p(a) + p(b) - p(a and b)
as you may know, p(a and b) is equal to p(a) * p(b).
if you don't yet, you will soon enough.
anyway, assuming these are independent, then p(a or b) is equal to p(a) + p(b).
based on this, the answers to your questions are:
servicability rating calculation probability
difficult or very difficult .11 + .16 .27
difficult or average or easy .16 + .35 + .28 .79
average or better .35 + .28 + .10 .73
average or better presumes average or easy or very easy.
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