Dexter
Dexter is an R package for psychometric analysis of data from educational and psychological tests. Dexter typically works with project database files saved on disk.
Installation
install.packages('dexter')
If you encounter a bug, please post a minimal reproducible example on github. We post news and examples on a blog, it's also the place for general questions.
Example
library(dexter)
# start a project and fill it with data
# verbAggrRules and verbAggrData are example datasets provided with dexter
db = start_new_project(verbAggrRules, "verbAggression.db")
add_booklet(db, verbAggrData, booklet_id = "verb_agg")
# Classical test theory
tia = tia_tables(db)
tia$testStats
| booklet_id | nItems | alpha | meanP | meanRit | meanRir | maxTestScore | N |
|---|
| verb_agg | 24 | 0.888 | 0.339 | 0.527 | 0.468 | 48 | 316 |
head(tia$itemStats)
| booklet_id | item_id | meanScore | sdScore | maxScore | pvalue | rit | rir | n |
|---|
| verb_agg | S1DoCurse | 1.082 | 0.808 | 2 | 0.541 | 0.582 | 0.519 | 316 |
| verb_agg | S1DoScold | 0.832 | 0.817 | 2 | 0.416 | 0.651 | 0.596 | 316 |
| verb_agg | S1DoShout | 0.468 | 0.710 | 2 | 0.234 | 0.520 | 0.460 | 316 |
| verb_agg | S1WantCurse | 1.123 | 0.828 | 2 | 0.562 | 0.537 | 0.468 | 316 |
| verb_agg | S1WantScold | 0.930 | 0.852 | 2 | 0.465 | 0.593 | 0.528 | 316 |
| verb_agg | S1WantShout | 0.712 | 0.778 | 2 | 0.356 | 0.529 | 0.464 | 316 |
# IRT, extended nominal response model
f = fit_enorm(db)
head(coef(f))
| item_id | item_score | beta | SE_b |
|---|
| S1DoCurse | 1 | -1.3422140 | 0.1541565 |
| S1DoCurse | 2 | -0.6375015 | 0.1418423 |
| S1DoScold | 1 | -0.6702036 | 0.1429057 |
| S1DoScold | 2 | -0.2589855 | 0.1579467 |
| S1DoShout | 1 | 0.3254326 | 0.1480166 |
| S1DoShout | 2 | 0.3687574 | 0.2099654 |
# ability estimates per person
abl = ability(db, parms = f)
head(abl)
| booklet_id | person_id | sumScore | theta |
|---|
| verb_agg | dxP1 | 13 | -1.0218323 |
| verb_agg | dxP10 | 9 | -1.4832759 |
| verb_agg | dxP100 | 14 | -0.9204799 |
| verb_agg | dxP101 | 0 | -Inf |
| verb_agg | dxP102 | 12 | -1.1276084 |
| verb_agg | dxP103 | 8 | -1.6191967 |
# ability estimates without item S1DoScold
abl2 = ability(db, parms = f, item_id != "S1DoScold")
# plausible values
pv = plausible_values(db, parms = f, nPV = 5)
head(pv)
| booklet_id | person_id | sumScore | PV1 | PV2 | PV3 | PV4 | PV5 |
|---|
| verb_agg | dxP1 | 13 | -0.8830828 | -0.7066814 | -0.7703465 | -1.0441590 | -0.8918823 |
| verb_agg | dxP10 | 9 | -1.5388849 | -1.0014150 | -1.7249607 | -1.3372498 | -1.5627987 |
| verb_agg | dxP100 | 14 | -0.6678893 | -1.4039775 | -0.6161149 | -0.9249503 | -0.7607182 |
| verb_agg | dxP101 | 0 | -2.3034185 | -3.0623911 | -2.3793639 | -3.1658178 | -3.3999772 |
| verb_agg | dxP102 | 12 | -1.0434515 | -1.5317991 | -1.1518701 | -1.0103475 | -1.0057779 |
| verb_agg | dxP103 | 8 | -2.0467553 | -1.5357100 | -2.0598186 | -1.2366479 | -1.7367032 |
Contributing
Contributions are welcome but please check with us first about what you would like to contribute.