Compute the parameters shape1 and shape2 of the beta distribution using method of moments given the mean and standard deviation of the random variable of interest.
mom_beta(mean, sd)
Arguments
mean: Mean of the random variable.
sd: Standard deviation of the random variable.
Returns
A list containing the parameters shape1 and shape2.
Details
If μ is the mean and σ is the standard deviation of the random variable, then the method of moments estimates of the parameters shape1 = α>0 and shape2 = β>0 are:
α=μ(σ2μ(1−μ)−1)
and
β=(1−μ)(σ2μ(1−μ)−1)
Examples
mom_beta(mean =.8, sd =.1)# The function is vectorized.mom_beta(mean = c(.6,.8), sd = c(.08,.1))