Classical analysis of item scores Flashcards
What three properties describe an item score distribution?
1) Location
2) Dispersion
3) Shape
What is meant by item difficulty and when is it used?
Item difficulty is a parameter in maximum performance tests. More test takers fail on more difficult items.
What parameter is used in typical performance tests?
Item attractiveness
Item difficulty/ Item attractiveness is equal to ________
Item mean
What causes a danger in small variances in items?
due to floor/ceiling effects in Likert scales (e.g. items with low attractiveness)
What is the effect of large item correlations in regards to the tests reliability?
Large item correlations result in high reliability.
What is meant by item discrimination?
how well a given item can distinguish between people that differ on the underlying construct.
What is meant by the item test correlation?
The item-test correlation is the correlation between the scores on a given item and the test scores. Items that discriminate well have a high item-test correlation.
What is meant by the item-rest correlation?
The item-rest correlation is the correlation between the scores on a given item and the rest score, the score without that item.
Why is the item-rest correlation calculated?
item-test correlation, correlation is biased upwards as you are correlating an item with itself. It uses the following formula:
What is the classic difficulty of a dichotomously scored multiple choice item?
The classical difficulty of a dichotomously scored multiple-choice item is the proportion of persons in a population who selected the correct answer to the item.
What is meant by the popularity of a distractor?
proportion of persons in a population who selected the distractor.
What is the item distracter-rest correlation?
The item distractor-rest correlation is the correlation between the correct answer / distractor variables and the rest score
What is meant by a positive distractor-rest correlation
indicates that that the distractor tends to attract test takers who have lower true scores than the test takers who selected the correct answer.
What does a negative distractor-rest correlation indicate?
A negative distractor-rest correlation indicates that the distractor tends to attract test takers who have higher true scores than the test takers who selected the correct answer.
