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

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

Formula Details for you !

n = number of trials x = number of successes n – x = number of failures s = probability of success in one trial f = 1 – s = probability of failure in one trial

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 trials x = number of successes n – x = number of failures s = probability of success in one trial f = 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