SOLUTION: The probability that student passes the SRA Exam is 0.71. Twelve students take the exam. Find each probability (to four decimal places) P( Exactly 6 pass the exam) this is ho

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Question 905632: The probability that student passes the SRA Exam is 0.71. Twelve students take the exam. Find each probability (to four decimal places)
P( Exactly 6 pass the exam)
this is how i set it up (12/6) (0.71)^6 (0.29)^6
could you help me out? I'm not sure exactly how to set it up and solve it
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
the 12/6 should be 12 C 6. This is referring to the combination formula

http://www.mathwords.com/c/combination_formula.htm

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n C r = (n!)/(r!(n-r)!)

12 C 6 = (12!)/(6!*(12-6)!)

12 C 6 = (12!)/(6!*6!)

12 C 6 = (12*11*10*9*8*7*6!)/(6!*6!)

12 C 6 = (12*11*10*9*8*7)/(6!)

12 C 6 = (12*11*10*9*8*7)/(6*5*4*3*2*1)

12 C 6 = (665280)/(720)

12 C 6 = 924
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So you should have this

(12 C 6)*(0.71)^6*(0.29)^6

(924)*(0.71)^6*(0.29)^6

0.0704060615439

Round that to 4 decimal places as instructed to get 0.0704

Therefore, P(Exactly 6 pass the exam) = 0.0704 (approximately)

This is roughly a 7.04% chance.

Here is a handy binomial distribution stats calculator

http://stattrek.com/online-calculator/binomial.aspx