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##### Statistics help with this equation: P(x)=C(n,x)s^xf^n-x

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I need someone to explain this to me. I know its for binomial distribution, but I can't figure out the C or how to plug this into the calculator. I just need someone to explain it to me because I want to know how to do it by hand as well. I have a TI-83

Oct 21st, 2017

# P(x)=C(n,x)s^xf^n-x

The probability of achieving exactly k successes in n trials is shown below.

 Formula Details for you ! n = number of trialsx = number of successesn – x = number of failuress = probability of success in one trialf = 1 – s = probability of failure in one trial

Apr 19th, 2015

how do I use the formula, though, could you do a sample problem?

Apr 19th, 2015

Ya definitly !

Apr 19th, 2015

You are taking a 10 question multiple choice test. If each question has four choices and you guess on each question, what is the probability of getting exactly 7 questions correct?

# P(x)=C(n,x)s^xf^n-x

The probability of achieving exactly k successes in n trials is shown below.

 Formula Details for you ! n = number of trialsx = number of successesn – x = number of failuress = probability of success in one trialf = 1 – s = probability of failure in one trial

n = 10
x = 7
n – x = 3

Applying the formula for probability distribution.
s = 0.25 = probability of guessing the correct answer on a question
f = 0.75 = probability of guessing the wrong answer on a question

Apr 19th, 2015

IK it sounds stupid but could u show work, I want to make sure I'm doing this right. thnx

Apr 19th, 2015

Yes I can....

# P(x)=C(n,x)s^xf^n-x

Since only one out ot 4 options can be right, probability of getting right = 0.25
Probability of getting wrong = 1 - 0.25 = 0.75
P(7 ) = C( 10,7) . ( 0.25 ) ^7  . ( 0,75 ) ^3

You may solve this now I suppose !!!

I hope I am a good tutor !!!

Apr 19th, 2015

one last thing could you solve it?

Apr 19th, 2015

Yes tell me !!!

I would appreciate if you make a separate bid for it !!!

I think the bid  amount is very less to answer so many questions !!!

It would be great on your part if you can pay me a little more !!!

Thank You !

Apr 19th, 2015

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Oct 21st, 2017
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Oct 21st, 2017
Oct 22nd, 2017
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