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whats the probability of six tails out of nine tosses?
probability
- Thread starter fancymylotus
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Topscore Test 1 QR. I missed it. I won't anymore though. 🙂
There's a formula:
Probability of r successes out of n attempts: (nCr) * (p^r) * (q^n-r)
p = probability of successes in a single trial
q = prob. of failure
nCr = (9x8x7x6x5x4)/(6x5x4x3x2x1) = 84
success = (1/2)^6 = 1/64
failures = (1/2)^3 = 1/8
Plug in all values into formula up top.
(84)(1/64)(1/8) = 21/128.
That's the way they explain it. There must be an easier way though?
There's a formula:
Probability of r successes out of n attempts: (nCr) * (p^r) * (q^n-r)
p = probability of successes in a single trial
q = prob. of failure
nCr = (9x8x7x6x5x4)/(6x5x4x3x2x1) = 84
success = (1/2)^6 = 1/64
failures = (1/2)^3 = 1/8
Plug in all values into formula up top.
(84)(1/64)(1/8) = 21/128.
That's the way they explain it. There must be an easier way though?
