R: Prior Cumulative Distribution Function (CDF)

pprior {abtest} | R Documentation

## Prior Cumulative Distribution Function (CDF)

### Description

Function for evaluating the prior cumulative distribution function (CDF).

### Usage

    pprior(
      q,
      prior_par = list(mu_psi = 0, sigma_psi = 1, mu_beta = 0, sigma_beta = 1),
      what = "logor",
      hypothesis = "H1"
    )

### Arguments

`q` | numeric vector with quantiles.
`prior_par` | list with prior parameters. This list needs to contain the following elements: `mu_psi` (prior mean for the normal prior on the test-relevant log odds ratio), `sigma_psi` (prior standard deviation for the normal prior on the test-relevant log odds ratio), `mu_beta` (prior mean for the normal prior on the grand mean of the log odds), `sigma_beta` (prior standard deviation for the normal prior on the grand mean of the log odds). Each of the elements needs to be a real number (the standard deviations need to be positive). The default are standard normal priors for both the log odds ratio parameter and the grand mean of the log odds parameter.
`what` | character specifying for which quantity the prior CDF should be evaluated. Either `"logor"` (i.e., log odds ratio) , `"or"` (i.e., odds ratio), `"rrisk"` (i.e., relative risk, the ratio of the "success" probability in the experimental and the control condition), or `"arisk"` (i.e., absolute risk, the difference of the "success" probability in the experimental and control condition).
`hypothesis` | character specifying whether to evaluate the CDF for a two-sided prior (i.e., "H1"), a one-sided prior with lower truncation point (i.e., "H+"), or a one-sided prior with upper truncation point (i.e., "H-").

### Value

numeric vector with the values of the prior CDF.

### Note

Internally, the test-relevant prior is always a normal prior on the log odds ratio, consequently, if `what` is not `"logor"`, the implied prior CDF for the quantity is returned.

### Author(s)

Quentin F. Gronau

### Examples

    # prior parameters
    prior_par <- list(mu_psi = 0, sigma_psi = 1,
                      mu_beta = 0, sigma_beta = 1)

    # evaluate prior CDF
    pprior(q = 0.1, prior_par = prior_par, what = "logor")
    pprior(q = 1.1, prior_par = prior_par, what = "or")
    pprior(q = 1.05, prior_par = prior_par, what = "rrisk")
    pprior(q = 0.02, prior_par = prior_par, what = "arisk")

    # also works for vectors
    pprior(q = c(-0.1, 0, 0.1, 0.2), prior_par = prior_par, what = "logor")

[Package abtest version 1.0.1 Index]