Science:Math Exam Resources/Courses/MATH103/April 2009/Question 01 (f)
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Question 01 (f) 

Multiple Choice question: Select ONE correct answer. You will not be graded for any work. Each mouse born with a certain genetic mutation has probability 0.7 of contracting a certain disease. Out of 10 mice born with the mutation, the probability that exactly 8 will contract the disease is (a) 45(.7)^{8}(.3)^{2} (b) 0.7(0.3)^{7} (c) 1/11 (d) 8/10 (e) 45/2^{10} 
Make sure you understand the problem fully: What is the question asking you to do? Are there specific conditions or constraints that you should take note of? How will you know if your answer is correct from your work only? Can you rephrase the question in your own words in a way that makes sense to you? 
If you are stuck, check the hints below. Read the first one and consider it for a while. Does it give you a new idea on how to approach the problem? If so, try it! If after a while you are still stuck, go for the next hint. 
Hint 1 

This is a bernoulli experiment. 
Hint 2 

The formula for probability , number of trials and success is
(Often is written as C(N,k).) 
Checking a solution serves two purposes: helping you if, after having used all the hints, you still are stuck on the problem; or if you have solved the problem and would like to check your work.

Solution 

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Please rate my easiness! It's quick and helps everyone guide their studies. By using the formula for the bernoulli experiment
for , and and get
So, the answer is (a). 