Alpha

Question 1

Standardized coeff alpha

Answer 1

aka Generalized spearman brown formula

• Same as raw apha but it uses standardized score (z-score)
• Standardized alpha is an estimate of reliability
• Correlation for each item combo is calculated (pairwise correlations)

used if eg the variance is very different

Question 2

KR20

Answer 2

Raw alpha for binary

Shows percentage of correct answer for each item. p is correct, q is incorrect

Question 3

Omega

Answer 3

Based on ratio of signal to noise

Strong factor loadings (close to true score, little noise)
Factor analysis is used to score factors, producing total signal allows calculation

Question 4

internal consistency vs unidemensionality

Answer 4

Important to differentiate between conceptually homogeneous items (unidimensional measure on 1 attribute)

Question 5

increasing reliability

Answer 5

Improving consistency among parts by;
- Rewriting some items to make them less ambiguous
- replacing items with more relavant items

= Greater internal consistency is greater reliability

Question 6

Length of the test

Answer 6

In CTT, longer tests have higher reliability, as increase of true score var means higher reliability
Similar to the function of a spearman formula in the split-half test

But;
- Important that it remains parallel, difficult to find consistent items
- Test taker fatique