---
title: "Examples: Credibility Intervals"
author: "Philip I. Pavlik Jr."
date: "2026-06-07"
output: rmarkdown::html_vignette
vignette: >
  %\VignetteIndexEntry{Examples: Credibility Intervals}
  %\VignetteEngine{knitr::rmarkdown}
  \usepackage[utf8]{inputenc}
---

```{r setup}
source("lkt-vignette-setup.R")
knitr::opts_chunk$set(eval = run_expensive_vignette)
```

The bootstrap is intentionally not evaluated during routine CRAN checks. Set
`LKT_RUN_EXPENSIVE_VIGNETTES=true` to execute it when rendering.

# Load data

```{r bundled-data}
val <- prepare_largeraw_sample()
```

# Credibility intervals

```{r credibility-model}
components <- c("KC..Default.", "KC..Default.", "KC..Default.")
features <- c("intercept", "linesuc$", "linefail$")
fixedpars <- NA

mod1 <- LKT(
  data.table::setDT(val),
  interc = TRUE,
  components = components,
  features = features,
  fixedpars = fixedpars,
  seedpars = c(NA)
)

check_lkt_fit(mod1, expected_r2 = 0.21369, expected_loglike = -29866.78674638)
check_has_coefficient_containing(mod1, ":linesucKC..Default.")
```

```{r credibility-bootstrap}
n_students <- 400
n_boot <- 100
boot_res <- LKT_HDI(
  val,
  n_boot,
  n_students,
  comps = components,
  feats = features,
  fixeds = fixedpars,
  cred_mass = 0.99
)

check_true("HDI bootstrap count", nrow(boot_res$par_reps) == n_boot)
check_true("HDI result rows", nrow(boot_res$coef_hdi) >= 20)
check_close("HDI credibility mass", boot_res$coef_hdi$credMass[1], 0.99)
```