Merge pull request #144 from jtimonen/master

correct y to n in NegBinomial2 density

Author: mcol

src/functions-reference/unbounded_discrete_distributions.Rmd

@@ -93,8 +93,8 @@ alternative parameterization directly in terms of the log mean.
 
 The first parameterization is for $\mu \in \mathbb{R}^+$ and $\phi \in
 \mathbb{R}^+$, which for $n \in \mathbb{N}$ is defined as \[
-\text{NegBinomial2}(n \, | \, \mu, \phi)  = \binom{n + \phi - 1}{y} \,
-\left( \frac{\mu}{\mu+\phi} \right)^{\!y} \, \left(
+\text{NegBinomial2}(n \, | \, \mu, \phi)  = \binom{n + \phi - 1}{n} \,
+\left( \frac{\mu}{\mu+\phi} \right)^{\!n} \, \left(
 \frac{\phi}{\mu+\phi} \right)^{\!\phi} \!. \]
 
 The mean and variance of a random variable $n \sim