Posted by tanya on .
Quiz has 6 questions. Each question has five possible answers,
only one of each 5 answers is correct.
If student randomly guesses on all six questions,
what is the probability to answer 2 questions right?
Tip: first, you have to define parameters of Binomial distribution:
n  how many trials/questions do you have
p  probability guessing right answer to each question
x  how many successes do you expect.
Then use Appendix Table or Excel function for Binomial distribution.
Answer

statistic 
MathMate,
Assuming the 6 questions are independent,
n=6 (questions)
p=probability of guessing the right answer (1/5)
x=exactly the number of successes over the 6 questions (2).
Look up the appendix table, or the Excel function to calculate the probability.
Alternatively, use the formula:
P(x) = C(n,x)*p^{x}*(1p)^{nx}
Where C(n,x) represents the number of combinations of taking n things, x at a time. 
statistic 
Mare,
.8

statistic 
Anonymous,
on a test midterm exam each multiple choice question provides five possible answers. what is the probability of randomly guessing three consecutive questions correctly?

statistic 
Anonymous,
.324

statistic 
Anonymous,
.24576
You're welcome 
geology 
abrham kussbilo,
0.24576

geology 
abrham kussbilo,
answer 0.24576

statistic 
abrham kussbilo,
p(x=4)=0.24576

statistic 
Xu,
p(x=4) = binompdf(6, 1/5, 4) = 0.2458