psycometrics

Eigenvalues

quantify factor strength

Scree plots

visualize eigenvalues to help decide how many factors to retain.

Coefficient alpha

gauges internal consistency, which tends to increase as the number of related items in a scale increases.

Systematic error

produces a predictable bias pushing scores consistently

random error

fluctuates unpredictably around the true score.

CONSTRUCT VALIDITY

Does a measure actually measure the construct it claims to

Internal consistency

if different items test a similar concept

test-retest reliability

average scores across all the items is the same each time it is taken

Inter-rate reliability

on open ended items, two or more coders agree on the meaning of the response

Factor analysis

tells us how many factors there are being measured on the questionnaire