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More on Measurement

More on Measurement. Recap. Measurement Operationalization Validity. Reliability. The extent to which a test, experiment, scale, etc. give the same results from one time to the next. Test retest method Alternate form Split Halves Interitem Association. Measuring Reliability.

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More on Measurement

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  1. More on Measurement

  2. Recap • Measurement • Operationalization • Validity

  3. Reliability • The extent to which a test, experiment, scale, etc. give the same results from one time to the next. • Test retest method • Alternate form • Split Halves • Interitem Association

  4. Measuring Reliability • Correlation matrix • Correlation • Measure of Association • Ranges from -1 to +1 • -1 is perfect negative relationship • 1 is perfect positive • 0 is absolutely no relationship • Cronbach’s Alpha (α) • Measures association of all items with scale • Ranges from 0-1 • Good Scales are >.6

  5. Challenges to Reliability • Changes in method of measurement over time • Extraneous factors • Forget to account for reverse coded items • Items really measure different things

  6. Level of Measurement • Nominal • Ordinal • Interval • Ratio

  7. Combining Items • It is often preferable to combine scores • Items may all represent same thing • Easier to deal with • Downside- • losing some information • Need similar items (reliability) • Need to cover relevant dimensions (construct validity)

  8. Indexes • Sum up items related to each other • Use sum as new number • Problem- Treats all items as equally important • Problem- often haphazard

  9. Scales • More systematic in choice of items • Likert Scale • Begin with agreement/Disagreement questions • Sum • Find items that differentiate highs from lows • Based on results from data, not researcher • Problems • Does not weight for importance • Not sure if all dimensions are covered • Cannot know what set of responses gives score

  10. Guttman Scale • Also determined by data • Start with easy and hard items • Look to see if they form patterns • Example- Political Participation • Voting • Button • Bumper Sticker • Yard Sign • Donating • Volunteering • We would expect people who do the harder activities to have done the easier ones as well. • Statistical Test to see how well Guttman Scaling applies

  11. Semantic Differential • More a type of question than a scaling technique • Ask respondent pairs of words (e.g. honest/dishonest) and have them rate item somewhere between two. • Can ask for multiple traits • Problem- confusing way to ask question

  12. An Example- The RWA Scale • Right Wing Authoritarianism • Measure of obedience, traditionalism, hostility towards outgroups • Conventionalism, Authoritarian Aggression, Authoritarian Submission • 34 items • Sum • Check reliability (high)

  13. Review

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