Posted by Tony on Wednesday, June 8, 2011 at 7:56pm.
A machine has 7 identical components which function independently. The probability that a component will fail is .2. The machine will stop working if more than three components fail. Find the probability that the machine will be working?

Elementary Statistics  Reiny, Wednesday, June 8, 2011 at 8:21pm
The machine will be working if
1. no part fails > (.8)^7
2. 1 part fails > C(7,1)(.2)(.8)^6
3. 2 parts fail > C(7,2)(.2^2)(.8^5)
4. 3 parts fail > C(7,3)(.2^3)(.8^4)
add them up 
Elementary Statistics  Anonymous, Saturday, June 25, 2016 at 3:55pm
.966