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)}/\left(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.