Week 11 and 12: Reliability and Validity Flashcards
Define reliability
Consistency in measurement
List 3 ways that consistency of scores occurs when re-examining the same people
- the same test on different occasions
- different set of items measuring the same thing
- different conditions of testing
What is standard error of measurement?
An estimate of the amount of error usually attached to an examinee’s obtained score
What is a confidence interval
Confidence that you have that the population mean is within that interval
What are some sources of random error?
- test construction
- test administration
- test scoring and interpretation
- test construction error
List the ways of testing reliability
- cronbach’s alpha
- test retest
- split half
- item total correlations
How big should a reliability coefficient be?
Above .8, preferably .9
What does cronbach’s alpha measure
A set of all possible correlations between test items
What is split half reliability
Taking half the items and seeing how they correlate with the other half
What are item total correlations
Getting the item and comparing it to the rest of the scale
What is test-retest reliability
- correlation between two testing intervals
- stability over time
- uses Pearson’s r
What are some problems with test-retest reliability
- affected by factors associated with how the test is administered on each occasion
- carryover effect: remember answer, practice effect
- should only be used for meaningful data
Internal consistency
The correlations between different items on the same test, or with the entire test
Kuder-richardson reliability and coefficient alpha
- based on the intercorrelations among all comparable parts f the test
Kuder-richardson formula 20
- calculated by the proportion of people who pass and fail each item and the variance of the test scores
Inter-rater reliability
- agreement through multiple raters
- measured using a kappa statistic
Kappa statistic
Measures inter rater agreement for qualitative (categorical) items
Parallel-forms reliability
Equivalent forms of the same test are administered to the same group
Types of reliability
- inter-rater
- test-retest
- split half
- parallel forms
Validity
The extent to which a test measures what it is supposed to measure