PPP {edina} | R Documentation |
Computes posterior predictive probabilities (PPPs) based on the odds ratios for each pair of items.
PPP(object, ...) ## S3 method for class 'edina' PPP(object, alpha = 0.05, ...)
object |
An |
... |
Not used. |
alpha |
Defining region to indicate the level of extremeness the data must before the model is problematic. |
PPPs that smaller than 0.05 or greater than 0.95 tend to be extreme and evidence of misfit. As a result, this is more of a heuristic metric.
The PPP value given the specified alpha
value.
simulate observed responses \mathbf Y^{(r)} using model parameters from iteration r of the MCMC sampler
computing the odds ratio for each pair of items at iteration r as
OR^{(r)} = n_{11}^{(r)}n_{00}^{(r)}/≤ft(n_{10}^{(r)}n_{01}^{(r)}\right)
, where n_{11}^{(r)} is the frequency of ones on both variables at iteration r, n_{10}^{(r)} is the frequency of ones on the first item and zeros on the second at iteration r, etc.; and
computing PPPs for each item pair as the proportion of generated OR^{(r)}'s that exceeded elements of the observed odds ratios.