Posted by **tanya** on Saturday, December 4, 2010 at 11:16pm.

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**, Sunday, December 5, 2010 at 8:54am
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}*(1-p)^{n-x}

Where C(n,x) represents the number of combinations of taking n things, x at a time.

- statistic -
**Mare**, Tuesday, October 25, 2011 at 11:48am
.8

- statistic -
**Anonymous**, Wednesday, October 17, 2012 at 1:39pm
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**, Tuesday, May 28, 2013 at 7:09pm
.324

- statistic -
**Anonymous**, Tuesday, December 8, 2015 at 6:27pm
.24576

You're welcome

- geology -
**abrham kussbilo**, Thursday, June 9, 2016 at 10:52am
0.24576

- geology -
**abrham kussbilo**, Thursday, June 9, 2016 at 10:55am
answer 0.24576

- statistic -
**abrham kussbilo**, Thursday, June 9, 2016 at 10:57am
p(x=4)=0.24576

- statistic -
**Xu**, Wednesday, November 30, 2016 at 4:25pm
p(x=4) = binompdf(6, 1/5, 4) = 0.2458

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