1. 8-1 Chapter Eight MEASUREMENT

2. 8-2 Measurement Selecting observable empirical events Using numbers (0, 1, #, %) or symbols (M, F, etc.) to represent aspects of the events Applying a mapping rule to connect the observation to the symbol

3. 8-3 What is Measured? Objects: –Things of ordinary experience (concrete) –Some things not concrete (attitude, emotion) Properties: characteristics of objects –Physical –Psychological –Social –Economic

4. 8-4 Characteristics of Data Classification (without order) Order Distance (interval between numbers) Unique origin of number series

5. 8-5 Data Types OrderIntervalOrigin Nominalnonenonenone Ordinalyesunequalnone Intervalyesequal ornone unequal Ratioyesequalzero

6. 8-6 Examples of Data Nominal: gender, religious preference, political affiliation, ethnic origin Ordinal: ranking, rating, doneness of meat Interval: temperature, calendar time Ratio: weight, height, income level, population

7. 8-7 Sources of Measurement Differences (Errors) Respondent (Participants) Situational factors Measurer (interviewer) Data collection instrument: defective instrument (e.g. confusing or ambiguous questions, limited coverage of content items)

8. 8-8 Elements of Sound Measurement Valid measurement –Accurate and precise measurement Reliable measurement –Consistent measurement (accurate and precise measurement procedure) Practical measurement

9. 8-9 Validity Content Validity: adequate coverage of investigative questions (can be determined by the designer or a panel of selected persons) Criterion-Related Validity: estimating and/or predicting accuracy. –Concurrent: estimation –Predictive: forecast Construct Validity: identifiability of underlying construct(s) (factor analysis)

10. 8-10 Reliability Reliability means “free from random or unstable error –Stability: consistency over time (Test- retest) –Equivalence: consistency across observers (Parallel forms) –Internal Consistency (homogeneity among similar question items) Split-half, KR20, Cronbach’s alpha Improving reliability?

11. 8-11 Practicality Economy: affordable Convenience: easy to administer Interpretability: easy to understand