qprior {abtest} R Documentation

## Prior Quantile Function

### Description

Function for evaluating the prior quantile function.

### Usage

```qprior(
p,
prior_par = list(mu_psi = 0, sigma_psi = 1, mu_beta = 0, sigma_beta = 1),
what = "logor",
hypothesis = "H1"
)
```

### Arguments

 `p` numeric vector with probabilities. `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 quantile function 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 quantile function 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 quantile function.

### 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 quantile function
qprior(p = .1, prior_par = prior_par, what = "logor")
qprior(p = .7, prior_par = prior_par, what = "or")
qprior(p = .9, prior_par = prior_par, what = "rrisk")
qprior(p = .7, prior_par = prior_par, what = "arisk")

# also works for vectors
qprior(p = c(.1, .2, .5, .7, .9), prior_par = prior_par, what = "logor")
```

[Package abtest version 1.0.1 Index]