Definitions Correlation, Reliability, Validity, Measurement error Theories of Reliability

1. Quality of Measures • Definitions • Correlation, Reliability, Validity, Measurement error • Theories of Reliability • Types of Reliability • Standard Error of Measurement • Types of Validity • Article • Exercise

2. Definitions • Correlation • reflect direction (+/-) & strength (0 to 1) of the relation between two variables • Variance explained • Reflects the strength of relation of two variables • Square of correlation • Varies from 0 to 1

3. Vince Carter Tom Cruise Julia Roberts Calista Flockhart

4. r = .76 r2 = 58% Vince Carter Tom Cruise Julia Roberts Calista Flockhart

5. Effect of Measurement Error on Correlations

6. r = 1.00 r2 = 100%

7. r = .98 r2 = 96%

8. r = .92; r2 = 85%

9. Definitions • Reliability • Consistency & stability of measurement • Reliability is necessary but not sufficient for validity • E.g. A measuring tape to is not a valid way to measure weight although the tape reliably measures height and height correlates w/weight • Validity • Accuracy/meaning of measurement • Example: unstructured vs. structured job interviews

10. Theories of Reliability • Classical Test Theory explains random variation in a person’s scores on a measure • Effects of learning, mood, changes in understanding etc. • Test score=true score + error • Errors have zero mean • Errors are uncorrelated with each other • Errors are uncorrelated with true score • Constant error is part of true score

11. Types of Reliability • Test-retest • Consistency across time • Parallel forms • Consistency across versions • Internal • Consistency across items • Scorer (inter-rater) • Consistency across raters/judges

12. Example: The Satisfaction with Life Scale (SWLS) 1. In most ways my life is close to ideal. 2. The conditions of my life are excellent.3. I am satisfied with my life.4. So far I have gotten the important things I want in my life.5. If I could live my life over, I would change almost nothing. 1 2 3 4 5 6 7Strongly StronglyDisagree Agree

13. Types of Reliability • Test-retest reliability • Correlation of scores on the same measure taken at two different times • Time interval assumes no memory/learning effects • Parallel-forms • Correlation of scores on similar versions of the measure • Forms equivalent on mean, stan dev, inter-correlations • Can have time interval b/w admin of two forms

14. Types of Reliability P=participant I=item

15. r = .73; r2 = 50%

16. Test-retest reliability of SWLS • Good test-retest reliability • Participants have similar scores at Time 1 (beginning of semester) and at Time 2 (end of semester). • Retest reliability is useful for constructs assumed to be stable • Current mood (e.g., how you feel right now) shows low-retest correlations, but that does not mean that the mood measure is not reliable

17. Types of Reliability • Internal Consistency • Correlation of scores on two halves of the measure • Length of measure increases reliability • Inter-rater • Correlation of raters’ scores • E.g., Scores on structured job interview • Can also include time interval • e.g., ratings of the worth of jobs across time & across judges

18. Types of Reliability

19. r = .70; r2 = 49%

20. Internal consistency of SWLS • Satisfactory internal consistency. • Participants respond similarly to items that are supposed to measure the same variable. • Should be .70 or higher • Measurement error accounts for half of the variance in SWLS scores.

21. Types of Reliability • Test-retest • Parallel forms • Internal • Scorer (inter-rater)

22. Standard Error of Measurement • SD of scores when a measure is completed several times by the same individual • Mostly used in selection contexts • Decide which of two individuals are hired • Decide whether a test score is significantly higher/lower than a cutoff score

23. Correction for Attenuation • Real correlation between two variables after removing unreliability of each measure • Divide observed correlation by product of the square roots of individual reliabilities • Note: Selection research only controls for unreliability in criterion bec. we are more interested in the value of the predictor given a perfectly reliable criterion

24. Quality of Measures • Definitions • Correlation, Reliability, Validity, Measurement error • Theories of Reliability • Types of Reliability • Standard Error of Measurement • Types of Validity

25. Validity • Evidence that a measure assesses the construct • Reasons for Invalid Measures • Different understanding of items • Different use of the scale (Response Styles) • Intentionally presenting false information (socially desirable responding, other-deception) • Unintentionally presenting false information (self-deception)

26. Types of Validity Construct Validity Criterion Validity Content Validity Predictive Validity Concurrent Validity Convergent Validity Discriminant Validity Adapted from Sekaran, 2004

27. Types of Validity • Content Validity • Extent to which items on the measure are a good representation of the construct • e.g., Is your job interview based on what is required for the job? • Content validity ratio based on judges’ assessments of a measure’s content • e.g., Expert (supervisors, incumbents) rating of job relevance of interview questions

28. Types of Validity • Criterion-related Validity • Extent to which a new measure relates to another known measure • Validity coefficient= Size of relation between the new measure (predictor) and the known measure (criterion) (a.k.a correlation) • e.g., do scores on your job interview predict performance evaluation scores?

29. Types of Criterion Validity • Concurrent • Scores on predictor and criterion are collected simultaneously (e.g., police officer study) • Distinguishes between participants in sample who are already known to be different from each other • Weaknesses • Range restriction • Does not include those who were not hired, fired & promoted • Differences in test-taking motivation (employees vs. applicants) • Experience with job can affect scores on criterion

30. Types of Criterion Validity • Predictive • Scores on predictor (e.g., selection test) collected some time before scores on criterion (e.g., job performance) • Able to differentiate individuals on a criterion assessed in the future • Weaknesses • Due to management pressures, applicants can be chosen based on scores on predictor (can have range restriction, but this can be corrected) • Often, special measures of job performance are developed for validation study

31. Correction for range restriction • When full range of scores on predictor variable is available • Use unrestricted and restricted standard deviations of predictor variable & the observed correlations b/w predictor & criterion

32. Types of Validity (cont’d) • Construct Validity • Extent to which hypotheses about construct are supported by data • Define construct, generate hypotheses about construct’s relation to other constructs • Develop comprehensive measure of construct & assess its reliability • Examine relationship of measure of construct to other, similar and dissimilar constructs • Examples: height & weight; Learning Style Orientation measure; networking; career outcomes

33. Establishing Construct Validity • Multi-trait multi-method matrix • Convergent validity coefficient • Absolute size of correlation between different measures of the same construct • should be large, significantly diff from zero, • Discriminant validity coefficient • Relative size of correlations between the same construct measured by different methods compared to • Different constructs measured by different methods • Different constructs measured by same method (method bias)

34. Corr b/w Objective (O) & Self-Reports (SR) of Height & Weight

35. Establishing Construct Validity • Multi-trait multi-method matrix • Different measures of the same construct should be more highly correlated than different measures of different constructs • e.g., Perceived career success & promotion vs. networking vs. promotion/salary • Different measures of different constructs should have lowest correlations • e.g., Networking vs. promotion/salary

36. Learning Style Orientation Measure • Item Development Study (generate critical incidents) • N=67 • Yes/no responses to statements • Recall of learning events • Two types of learning: theoretical, practical • Two types of outcomes=success, failure • 2 x 2 events per participant • 112 items constructed in total

37. Learning Style Orientation Measure • Item Development Study (questionnaire) • N=154 • 112 items, 5 point likert scale (agree/disagree) • 5 factor solution w/factor analyses • 54 items • Content validity sorting by 8 grad students • Goldberg personality scale

38. Learning Style Orientation Measure • Item Development Study • Correlations b/w LSO & personality • Only 1 sig correlation b/w 5 factors of LSOM! • High reliabilities of subscales of LSOM (.81-.91) • Construct (not really convergent) validity • r b/w LSOM & personality subscales • .42 to -.26.

39. Learning Style Orientation Measure • Validation Study • N=350 -193 • LSOM, Personality, old LSI, preferences for instructional & assessment methods • Construct validity • r b/w LSOM subscales & old LSI= .01 to .31 • r b/w LSOM & personality subscales= .01 to .55 • Confirmatory factor analysis • 5-dimensions confirmed • High reliability

40. Learning Style Orientation Measure • Validation Study • Incremental validity • Additional variance explained (LSOM vs LSI)

41. In-class Exercise • Brainstorm constructs to develop measures • E.g. Dimensions of CIR professor effectiveness, CIR student effectiveness • Choose two constructs that can be measured similarly and be defined clearly • Example measures • Self-report (rating scales) • Peer/informant reports • Observation • Archival measures • Trace measures etc etc.

42. In-class Exercise • Form two-person groups to • Generate items of the 2 different measures for each of the two constructs • Appointed person collects all items for both measures for both constructs • Compiles & distributes measures to class • Class gathers data on both measures & both constructs • Class enters data into SPSS format • Compute reliabilities,means, correlations

43. Fill in the correlations C1 C2 M1 M1 M2 M2

44. Types of Validity Construct Validity Criterion Validity Content Validity Predictive Validity Concurrent Validity Convergent Validity Discriminant Validity Adapted from Sekaran, 2004