A few days ago
Help with a probability question please!!?!?!?
The final test for a stats test is based on 18 different topics and the instructor announces in the class that the exam will have 6 question from six different topics. A student decides to only study 12 topics. What is the probability that from the topics the student studies:
a).No questions are asked?
b).Two questions are asked?
c).All six questions are asked?
Top 2 Answers
A few days ago
Favorite Answer
Let X be the number of question in a topic area the student studied.
X has the binomial distribution with n = 6 trials and success probability p = 12/18 = 2/3
In general, if X has the binomial distribution with n trials and a success probability of p then
P[X = x] = n!/(x!(n-x)!) * p^x * (1-p)^(n-x)
for values of x = 0, 1, 2, …, n
P[X = x] = 0 for any other value of x.
a)
P(X = 0) = 6!/(0! (6 – 0)!) * (2/3) ^ 0 * (1 – 2/3) ^ (6-0)
= 0.001371742
b)
P(X = 2) = 6!/(2! (6 – 2)!) * (2/3) ^ 2 * (1 – 2/3) ^ (6-2)
= 0.082304527
c) P(X = 6) = 6!/(6! (6 – 6)!) * (2/3) ^ 6 * (1 – 2/3) ^ (6-6)
= 0.087791495
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A few days ago
This is homework *help* — all you’ve done so far is to post the entire problem. Where are you stuck? If it’s simply with the application, think of the 18 topics as colored balls in a bag. Think of the six the student studies as bright red balls; the other twelves are a painfully dull gray. Now can you translate the problem into something like you’ve seen in your textbook? If not, write again and let us know where you’re stuck.
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