Question 1159924: 1. A school’s faith awareness group consists of 15 students and 3 teachers. If four members of the group are randomly chosen to go on a retreat, determine the probability of selecting three students.
2. a. Determine the probability distribution, in table form and graphical form, for the number of students selected to be in a six-person fund-raising committee from 9 students and 11 teachers.
b. What is the expected number of students on the committee?
Answer by Boreal(15235)   (Show Source):
You can put this solution on YOUR website! the total number of ways to select 4 from 18 is 18C4, and that is the denominator
the numerator for 3 students is 15C3 *3C1 for the teacher. Note the left of C add up to the left of C in the denominator, and the same to the right of C.
=455*3/3060=0.4461 probability of selecting 3 students.
for 0, it is 9C0*11C6/20C6=462/38760=0.0119
for 1, it is 9C1*11C5/38760=4158/38760=0.1073
for 2, 11880/38760=0.3065
for 3, 9C3*11C3/38760=0.3576
for 4, 9C4*11C2/38760=6940/38760=0.1788
for 5, 9C5*11C1/38760=0.0358
for 6, probability is 0.0022
expected value of students is sum of number * probability
=0+0.1073+.6130+1.0728+0.7032+0.1790+0.0132=2.6885 students.
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