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On the other hand, if such a tiling uses exactly k of the 2 × 1 tiles, then it uses n − 2k of the 1 × 1 tiles, and so uses n − k tiles total. There are ( n − k k ) {\displaystyle {\tbinom {n-k}{k}}} ways to order these tiles, and so summing this coefficient over all possible values of k gives the identity.
Random variables are usually written in upper case Roman letters, such as or and so on. Random variables, in this context, usually refer to something in words, such as "the height of a subject" for a continuous variable, or "the number of cars in the school car park" for a discrete variable, or "the colour of the next bicycle" for a categorical variable.
Cohen's kappa measures the agreement between two raters who each classify N items into C mutually exclusive categories. The definition of is =, where p o is the relative observed agreement among raters, and p e is the hypothetical probability of chance agreement, using the observed data to calculate the probabilities of each observer randomly selecting each category.
Expanding (x + y) n yields the sum of the 2 n products of the form e 1 e 2... e n where each e i is x or y. Rearranging factors shows that each product equals x n−k y k for some k between 0 and n. For a given k, the following are proved equal in succession: the number of terms equal to x n−k y k in the expansion
5.1.14 Arrows. 5.1.15 ... and some readers may not have any font which includes certain uncommon symbols. Spaces within a formula must be directly ... {k=1} k ^ 2}{a}
Since the probabilities must satisfy p 1 + ⋅⋅⋅ + p k = 1, it is natural to interpret E[X] as a weighted average of the x i values, with weights given by their probabilities p i. In the special case that all possible outcomes are equiprobable (that is, p 1 = ⋅⋅⋅ = p k), the weighted average is given by the standard average. In the ...
Pearson's correlation coefficient is the covariance of the two variables divided by the product of their standard deviations. The form of the definition involves a "product moment", that is, the mean (the first moment about the origin) of the product of the mean-adjusted random variables; hence the modifier product-moment in the name.
The styled characters are mostly located in the Mathematical Alphanumeric Symbols block, but the 24 characters in cells with a pink background are located in the letterlike symbols block, for example, ℛ (script capital r) is at U+211B rather than the expected U+1D4AD which is reserved.