Психометрика и конструирование тестов
Введено| English | Значение |
|---|---|
| construct validity/ˈkɒnstrʌkt væˈlɪdɪti/ | конструктивная валидность |
| standard error of measurement/ˈstændəd ˈerə ɒv ˈmeʒəmənt/ | стандартная ошибка измерения |
A decision before an answer
- A scale can be perfectly consistent and still measure the wrong thing.
- Your goal: Distinguish reliability types by the design that produced them.
Name reliability by design
- Reliability is consistency, and its type is named by the design that produced it: the same test twice gives test-retest reliability; two similar forms give alternate-forms reliability; consistency within one sitting (split-half, Cronbach alpha) is internal consistency; agreement between scorers is inter-rater reliability.
- The Spearman-Brown formula r_full=2r/(1+r) rescales a half-test correlation to full test length: r=.80 becomes about .89.
Odd and even halves of a test correlate r=.80. After Spearman-Brown correction, the estimated full-test reliability is about:
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r_full=2r/(1+r)=1.6/1.8≈.89.
Separate the validity types
- Validity is evidence for the proposed interpretation, not of the test itself: content validity asks whether items cover the domain; criterion validity relates scores to an outcome, concurrently or predictively; construct validity assembles convergent and discriminant evidence that the score tracks the intended trait.
- Reliability caps validity but never establishes it: a consistent scale can systematically measure something else.
Evidence that a score tracks the intended trait rather than a different one is primarily:
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Construct validity rests on convergent and discriminant evidence; the others are reliability or sampling properties.
Standardise the scores
- Standard scores re-express raw scores against a norm group: z=(X−mean)/SD, T=50+10z, and Wechsler deviation IQ=100+15z. A z of +2 gives IQ 130 and about the 98th percentile.
- The standard error of measurement SEM=SD×sqrt(1−r) converts reliability into a score band: SD=15 with r=.91 gives SEM=15×sqrt(.09)=4.5.
Two similar vocabulary tests given a week apart with r=.90 show alternate-forms reliability, not test-retest, because the form changed. With SD=15 and reliability .91, SEM=4.5 points. A z of +2 corresponds to IQ 130. A split-half correlation of .80 corrects to 2×.80/1.80≈.89 at full length.
A Wechsler score of 130 corresponds to z=____.
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130=100+15z gives z=2.
Analyse the items
- Item analysis checks each item: difficulty p is the proportion answering correctly, and discrimination is the item-total correlation.
- Items that nearly everyone or no one answers correctly carry little information; negative discrimination flags a likely miskeyed or misleading item.
Calling a two-different-forms correlation test-retest reliability, or citing high reliability as if it were validity evidence.
Какой ответ подходит к данному случаю?
Различайте виды надежности в зависимости от дизайна, который их дал
A highly reliable test must be valid for its stated purpose.
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Consistency does not establish that the intended interpretation is correct.
Keep the distinctions
- standard error of measurement 测量标准误 — The expected spread of observed scores around the true score, SD×sqrt(1−r).
- construct validity 构想效度 — Convergent and discriminant evidence that a score reflects the intended trait.
- Distinguish reliability types by the design that produced them.
- Separate content, criterion and construct validity evidence.
- Compute standardised scores and the standard error of measurement.
Match each term with its precise meaning in this lesson.
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Keep the distinctions stated in the teaching example.
Put this lesson’s reasoning or event sequence in order.
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The order follows the stated process; check each stage before the next.