You can
put this solution on YOUR website! Suppose we want to determine the (binomial) probability (p) of getting 6 heads in 13 flips of a 2-sided coin.
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The 6 heads can show up is 13C6 = 1716 mutually exclusive ways.
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Each of those ways has probability (1/2)^6*(1/2)^7 = 1/2^13 = 1/8192
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Because the 1716 ways to succeed are mutually exclusive you should
add all 1716 of those separate probabilities to get the final probability.
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You could add but it's easier to just multiply 1716*(1/8192) = 0.2095
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In general, if there are n trials, and the probability of success
on each trial is "p", the probability of "k" successes is as follows:
P(x = k) = nCk*p^k*q^(n-k)
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Cheers,
stan H.
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