Course
Psychometrics
How a measurement of an unobservable construct is judged: what makes scores stable, and what would make an interpretation of them defensible.
Finishing this course means you have demonstrated the required skills with the level of support this course currently assesses.
- Modules
- 1
- Lessons
- 3
- Skills
- 3
- Starting here
- Assumes 2 prior topics
The route
Module 1: Reliability and validity
The observed score as a true score plus error, the coefficient computed from item variances and what it responds to, why it does not establish the number of dimensions, and what a validity claim requires beyond any coefficient.
- Given a reliability coefficient and the score standard deviation, the learner can compute the standard error of measurement, state the band an individual score carries and the assumptions that band rests on, and attribute the coefficient to scores from a population rather than to the instrument.
- Given item and total-score variances, the learner can compute coefficient alpha, state the measurement model under which it estimates reliability and when the lower-bound reading is available, apply the Spearman-Brown relation to separate item quality from test length, and decline to read dimensionality off the coefficient.
- Given a proposed use of test scores, the learner can state the interpretation the use relies on, name the kinds of evidence that would bear on it, and explain why reliability bounds a validity coefficient without supplying validity and why evidence for one use does not transfer to another.
What finishing means
Finishing this course means you have demonstrated the required skills with the level of support this course currently assesses.
3 required skills. If you reach a lesson without the background it assumes, you are pointed at the prerequisite first, and returned here afterwards.
How progress is measured
Progress is inferred from evidence you produce, not from pages you have opened. Each required skill moves through states as evidence accumulates: met, practicing with help, performed unassisted, then performed again after a delay.
This course counts a skill as finished atguided. Where the system cannot admit evidence for a stronger claim — for instance when the only available scoring is your own judgment of your written answer — the skill stays at the state the evidence supports, and the reason is shown rather than hidden.