Detailed Learning Objectives 1. Recognize the difference between a conceptual variable and its operationalization. 2. List three ways psychologists typically operationalize variables: self-report, observational, and physiological. 3. Classify variable scales as categorical or quantitative. 4. Describe the difference between the validity and the reliability of a measure. 5. Identify three types of reliability (test-retest, interrater, and internal), and know when each type is relevant.
Detailed Learning Objectives 6. Review scatterplots, focusing on how scatterplots show the direction and strength of a relationship. 7. Apply the correlation coefficient, r, as a way to describe the direction and strength of a relationship. (In this chapter, r is relevant as a common statistic to describe reliability and validity.) 8. Identify face and content validity. 9. Identify predictive, concurrent, convergent, and discriminant validity. 10. Describe how scatterplots, r, and known groups can be used to evaluate predictive, concurrent, convergent, and discriminant validity.
Conceptual and operational variables Three common types of measures Scales of measurement
Constructs and Operationalizations Three types of operationalization – Self-report – Observational – Physiological 5-item scale Well-being No. of smiles Brain scan Construct Operationalization
Scales of Measurement Categorical Quantitative – Ordinal (meaningful values but unequal intervals between units) – Interval (equal intervals between units but no meaningful zero) – Ratio (equal intervals and a meaningful zero)
The claim: “College students are getting more narcissistic.” Discussion starter
NPI Example Items: Forced-Choice Format (Ames, Rose, & Cameron, 2006) Narcissistic response I know that I am good because everybody keeps telling me so. I like to be the center of attention. I think I am a special person. I insist upon getting the respect that is due me. Everybody likes to hear my stories. I am going to be a great person. Non-narcissistic response When people compliment me I sometimes get embarrassed. I prefer to blend in with the crowd. I am no better nor no worse than most people. I usually get the respect that I deserve. Sometimes I tell good stories. I hope I am going to be successful.
When is each kind of reliability necessary? Why is reliability an empirical question? What does reliability tell us? Test-retest reliability Interrater reliability Internal reliability
Test-Retest Reliability: Consistent scores every time we test
Interrater Reliability: Consistent scores no matter who is rating
Interrater Reliability Example Demo of interrater reliability Pair up: Three kids 0:38 to 2:02 Girl in pink Girl in yellow Girl in blue Two people in each group count: How many times does she look away from the teacher? How many times does she clap? How many times does she put her hands in her lap?
Internal Reliability: Consistent scores no matter how you ask
Internal Reliability Internal reliability (not to be confused with internal validity!) The extent to which multiple measures, or items, are all answered the same by the same set of people. Cronbach’s alpha: An average of all of the possible item-total correlations.
I know that I am good because everybody keeps telling me so. I like to be the center of attention. I think I am a special person. I insist upon getting the respect that is due me. Everybody likes to hear my stories. I am going to be a great person. When people compliment me I sometimes get embarrassed. I prefer to blend in with the crowd. I am no better nor no worse than most people. I usually get the respect that I deserve. Sometimes I tell good stories. I hope I am going to be successful. Narcissistic responseNon-narcissistic response “The NPI-16 had an alpha of.72, while the full 40-item measure revealed an alpha of.84” (Ames et al., 2006, p. 442).
Measurement validity of abstract constructs Face validity and content validity Predictive validity and concurrent validity Convergent validity and discriminant validity Relationship between reliability and validity
Homework: Reliability What kind(s) of reliability would need to be evaluated? Draw a scatterplot or describe a result that would indicate that the measure has good reliability and one that shows it has poor reliability. 1. Researchers place unobtrusive video recording devices in the living rooms of 20 children. Later, coders view tapes of the living areas and code how many minutes each child spends playing video games. 2. Clinical psychologists have developed a 7- item self-report measure to quickly identify people who are at risk for panic disorder. 3. A restaurant owner uses a response card with four items in order to evaluate how satisfied customers are with the food, service, ambience, and overall experience.
Homework: Validity How might you show that this measure has predictive validity? How might you show that this measure has convergent and discriminant validity? 4.Clinical psychologists have developed a 7-item self-report measure to quickly identify people who are at risk for panic disorder. 5.A restaurant owner uses a response card to evaluate how satisfied customers are with the food. It contains one item, “Please rate the quality of the food:” on a scale from 1 (very dissatisfied) to 4 (very satisfied).
Relationship Between Reliability and Validity Can a measure be reliable but not valid? Examples: Shoe size as an intelligence test (reliable, not valid) Number of children you have as a measure of interest in children (reliably measured, but correlated with interest?) Can a measure be valid but not reliable? (No) Reliable and valid Reliable but not valid Not reliable and not valid
Reliability Is Necessary, But Not Sufficient for, Validity
Diener’s measure of happiness Gallup poll’s measure of happiness
Ames et al. (2006, p. 444) What kind of validity are these correlations supporting? Correlations of the 16-item NPI with: 40-item NPI:.90** Extraversion:.36** Agreeableness:-.23** Self-esteem:.30** Belief in a just world:.04
Reliability in articles “The NPI-16 had an alpha of.72, while the full 40-item measure revealed an alpha of.84” (Ames et al., 2006, p. 442).