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Counting: permutations and combinations
Factorials, ordered and unordered selections.
n! counts the orderings of n things. Choosing k of them in order is n!/(n − k)!; ignoring the order divides by k! again, giving the binomial coefficient “n choose k”. These numbers are Pascal's triangle and the coefficients of (a + b)ⁿ.
Δουλεμένο παράδειγμα · 5 choose 2
Βήμα προς βήμα
- \binom{5}{2} = \frac{5!}{2!\,(5-2)!}
Unordered selections: n! / (k! (n−k)!).
- = \frac{120}{2 \times 6} = 10
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Πώς να: Counting: permutations and combinations
- Unordered selections: n! / (k! (n−k)!).
Ερωτήσεις που κάνουν οι άνθρωποι
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The probability of seeing data at least this extreme if the null hypothesis were true. It is not the probability that the null hypothesis is true.
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