findbetaqq {PriorGen}

The findbetaqq function

Description

A function to estimate the parameters alpha and beta of a Beta distribution based on the existing prior belief (data and/or expert opinion) about the values of two distinct percentiles.

Usage

findbetaqq(percentile.value1, percentile1,
percentile.value2, percentile2, seed = 280385, nsims=10000)

Arguments

percentile.value1

specify the value for the first percentile. It takes a value between 0 and 1.

percentile1

specify which is the percentile that corresponds to percentile.value1. It takes a value between 0 and 1.

percentile.value2

specify the value for the second percentile. It takes a value between 0 and 1.

percentile2

specify which is the percentile that corresponds to percentile.value2. It takes a value between 0 and 1.

seed

A fixed seed for replication purposes.

nsims

Number of simulations for the creation of various summary metrics of the elicited prior.

Value

parameters: The beta distribution parameters Beta(a,b)

summary: A basic summary of the elicited prior

input: The initial input value that produced the above prior.

References

Kostoulas, P., Nielsen, S. S., Branscum, A. J., Johnson, W. O., Dendukuri, N., Dhand, N. K., Toft, N., Gardner, I. A. (2017): Reporting guidelines for diagnostic accuracy studies that use Bayesian latent class models (STARD–BLCM). Statistics in medicine, 23, 3603–3604.

Examples

## We believe that 20% of the units in an area/region have a prevalence of
## disease/infection less than or equal to 0.30 while at the same time
## we are 90% certain that the prevalence is less than 0.60

findbetaqq(
  percentile.value1 = 0.30, percentile1 = 0.20,
  percentile.value2 = 0.60, percentile2 = 0.90
)