The professor informs the class that there will be a test next week. What is the probability that a randomly
selected student studied for the test if they pass it with
a B or higher?
At the beginning of the semester, a professor tells
students that if they study for the tests, then there is a
55% chance they will get a B or higher on the tests. If
they do not study, there is a 20% chance that they will
get a B or higher on the tests. The professor knows
from prior surveys that 60% of students study for the
tests. The probabilities are displayed in the tree
diagram
O 0.20
O 0.55
O 0.60
O 0.80

the answer   is 200

step-by-step explanation:

this is a problem about poisson probabilities.   i don't know if you've

already studied poisson distributions, or if you have a place to look

to read more about the subject.  

here's how you can see a poisson distribution coming.   when there are

a lot of events that may happen at any time (or any place), and when

you're counting how many of them happen at a particular time (or a

particular place), and each event is independent of the others, then

the result is a poisson distribution.   this is roughly true for the

chocolate chips; one chip being in a cookie has only a small effect on

the probability that another chip will be in the cookie.

once you know you have a poisson distribution, you know a lot.   there

is only one parameter to a poisson distribution, so if you know the

mean, you know everything.   the form of the distribution is

  probability of n chips = {[e^(-x)]*(x^n)} / (n! )

the 3rd on is correct

step-by-step explanation:

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step-by-step explanation: