pri_par_adjust_static {sl4bayesmeta}R Documentation

Static prior tail-adjustment

Description

Adjusts the scale parameter of the half-normal, exponential, half-Cauchy and Lomax distributions such that the probability mass above the reference threshold equals the given tail probability. The shape parameter of the Lomax distribution is fixed at 1.

Usage

pri_par_adjust_static(UU=1, tail_prob=0.05)

Arguments

UU

reference threshold

tail_prob

probability mass of the prior above the reference threshold

Details

The condition imposed on the distribution is Pr[x > UU] = alpha, where alpha denotes the tail probability tail_prob.

To find a prior for the heterogenity standard deviation, the standard approach for outcomes on the log-odds ratio scale is to take the tail probability alpha = 5 % (tail_prob=0.05) and thresholds UU=1 or UU=2 (Spiegelhalter et al. 2004, Neuenschwander et al. 2010). For the half-normal distribution, these conditions lead to the HN(0.5) and HN(1) prior, respectively.

Value

A list of four scale parameter values (one for each prior considered):

p_HN

parameter of half-normal prior

p_EXP

parameter of exponential prior

p_HC

parameter of half-Cauchy prior

p_LMX

scale parameter for Lomax prior with shape parameter=1

References

Neuenschwander, B., Capkun-Niggli, G., Branson, M., Spiegelhalter, D. (2010). Summarizing historical information on controls in clinical trials. Clinical Trials 7(1), 5–18. https://doi.org/10.1177/1740774509356002

Spiegelhalter, D., Abrams, K., Myles, J. (2004). Bayesian Approaches to Clinical Trials and Health-Care Evaluation. John Wiley & Sons, Ltd.

See Also

pri_par_adjust_dynamic

Examples

# 5 % tail-adjustment
pri_par_adjust_static(UU=1)
pri_par_adjust_static(UU=2)

[Package sl4bayesmeta version 0.3-1 Index]