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You have a 5question multiplechoice test. Each question has four choices. You don’t know any of the answers. What is the experimental probability that you will guess exactly three out of five questions correctly?
 one year ago
 one year ago
You have a 5question multiplechoice test. Each question has four choices. You don’t know any of the answers. What is the experimental probability that you will guess exactly three out of five questions correctly?
 one year ago
 one year ago

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CliffSedgeBest ResponseYou've already chosen the best response.1
To get the experimental probability, you have to run the experiment.
 one year ago

kcla1996Best ResponseYou've already chosen the best response.0
can i just do it by writing a binomial
 one year ago

CliffSedgeBest ResponseYou've already chosen the best response.1
Yes, this is a binomial situation.
 one year ago

CliffSedgeBest ResponseYou've already chosen the best response.1
Consider the probability of success for each trial, the number of trials, the number of successes sought, and the number of combinations of getting that many successes.
 one year ago

kcla1996Best ResponseYou've already chosen the best response.0
10*9/4^3 this is what i got.....
 one year ago

CliffSedgeBest ResponseYou've already chosen the best response.1
Mmm, some of those numbers are right, but aren't in the right places...
 one year ago

satellite73Best ResponseYou've already chosen the best response.0
exactly 3 right out of 5 means 3 right, 2 wrong and \(\dbinom{5}{2}\) ways to do it
 one year ago

CliffSedgeBest ResponseYou've already chosen the best response.1
Number of ways to get 3 out of 5 = 5C3 = 5C2 = 10, so the 10 in right.
 one year ago

CliffSedgeBest ResponseYou've already chosen the best response.1
... *is right. 3 successes = (.25)^3 with a 25% chance of getting any question correct at random. 2 failures = (.75)^2 for similar reasons as above.
 one year ago

kcla1996Best ResponseYou've already chosen the best response.0
so can you help me write the answer?
 one year ago

CliffSedgeBest ResponseYou've already chosen the best response.1
See http://stattrek.com/probabilitydistributions/binomial.aspx?Tutorial=Stat for derivation of the binomial formula.
 one year ago

CliffSedgeBest ResponseYou've already chosen the best response.1
I think you have everything you need; just multiply it all together.
 one year ago

CliffSedgeBest ResponseYou've already chosen the best response.1
There are ten ways to get 3 out of 5. (use combinations formula 5choose3) To get 3 successes with a 25% chance each, that's 0.25 × 0.25 × 0.25 = (0.25)^3 To also get the 2 failures with a 75% chance: 0.75 × 0.75 = (0.75)^2 Altogether, the probability is 10 × (0.25)^3 ×(0.75)^2.
 one year ago

kcla1996Best ResponseYou've already chosen the best response.0
is 10 x (.25)^3 x(0.75)^2 the answer
 one year ago

CliffSedgeBest ResponseYou've already chosen the best response.1
Makes sense to me. 10 ways to have 3 successes and 2 failures multiplied by the probability of having 3 successes multiplied by the probability of having 2 failures. See also http://stattrek.com/probability/probabilityrules.aspx?Tutorial=Stat
 one year ago

CliffSedgeBest ResponseYou've already chosen the best response.1
Does it make sense to you? Why do you still have doubts? Follow those links to that website I posted and study until you understand why the probability is computed that way.
 one year ago
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