The probability of getting at least 1 answer correct = 1 - Probability of getting all answers correct.
So in your case it for be P(at least 1 answer correct) = 1 - 1/256
where 256 is your sample space, |S| = 2^8.
The probability of correct true & false question is 1/2 and the probability correct multiple choice (four answer) question is 1/4. We want the probability of correct, correct, and correct. Therefore the probability all 3 questions correct is 1/2 * 1/2 * 1/4 = 1/16.
4/25
5 out of 10
64/256
The probability of getting at least 1 correct answer is equal to one minus theprobability of answering all incorrect, this would be;P(atleast 1 correct) =1 - P(allincorrect) =1 - (1/2)8 =1 - 0.00390625 ~~ 0.9961 ~ 99.61%
The probability of correct true & false question is 1/2 and the probability correct multiple choice (four answer) question is 1/4. We want the probability of correct, correct, and correct. Therefore the probability all 3 questions correct is 1/2 * 1/2 * 1/4 = 1/16.
If there are four possible answers to a question, then a guessed answer would have a probability of 1 in 4. If there are six questions, then the mean number of correct answers would be six times 1 in 4, or 1.5
4/25
2
5 out of 10
64/256
Since there are only two options for the answer, on average the student will answer half of the answers correctly.
25
Depends on the questions, and how they are answered. T/F, multiple choice, matching, essay, etc. Could be randomly answering, making educated guesses, or applying some amount of knowledge on the subject. Each of these impacts the probability of supplying correct answers.
The probability of getting a perfect score in a three-question true or false quiz is 100% if you studied and retained the subject matter and the questions addressed that subject. If, however, you did not study, and you made pure guesses without any bias towards an answer partially based in your (now rather poor) knowledge, then the probability of getting any one question correct is 50%, so the probability of getting all three questions correct is 50% to the third power, or 12.5%.
The probability that she gets exactly 3 right is 8C3*(1/3)3*(2/3)5 = 0.2731 approx.
7/128, or about 5.5% The student has a 1/2 probability of getting each question correct. The probability that he passes is the probability that he gets 10 correct+probability that he gets 9 correct+probability that he gets 8 correct: P(passes)=P(10 right)+P(9 right)+P(8 right)=[(1/2)^10]+[(1/2)^10]*10+[(1/2)^10]*Combinations(10,2)=[(1/2)^10](1+10+45)=56/1024=7/128.