SOLUTION: I am a 12th grade statistics student I am having a hard time understanding my teacher. I was given a work sheet with the following question. a formula but no real instructions. The

Question 727550: I am a 12th grade statistics student I am having a hard time understanding my teacher. I was given a work sheet with the following question. a formula but no real instructions. The question is Assume that phone operators give out the correct number 75% of the time. What is the probability of getting 5 correct numbers, if you call the operators 8 times? Can you please help me with instructions on setting the formula up and maybe a simpler way for me to grasp the subject. Thank you Fatimah Sabb
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
The question is Assume that phone operators give out the correct number 75% of the time. What is the probability of getting 5 correct numbers, if you call the operators 8 times? Can you please help me with instructions on setting the formula up and maybe a simpler way for me to grasp the subject.
----
# of ways to get 5 correct in 8 calls: 8C5 = (8*7*6)/(1*2*3) = 56
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Note: each of those 56 patters of 5 correct and 3 incorrect has
probability 0.75*5*0.25^3 = 0.2373*0.0156 = 0.0037
----
Since each of the 56 correct/incorrect patterns are mutually exclusive
you have to add their probabilities to get:
----
P(5 correct in 8 calls) = 56*0.0037 = 0.2976
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Note: I've shown you all the pieces. the answer is
usually written as follows:
p(x = 5 out of 8) = 8C5*(0.75)^5*(0.25)^3
=============================================
Cheers,
Stan H.
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