CHAPTER 3

1. CHAPTER 3 Three Claims, Four Validities: Interrogation Tools for Consumers of Research

2. Detailed Learning Objectives 1. Identify variables and distinguish a variable from its levels (or values). 2. Discriminate between measured and manipulated variables. 3. Describe a variable in terms of both its conceptual definition and its operationalization. 4. Indicate how many variables frequency, association, and causal claims typically involve. 5. Describe positive, negative, zero, and curvilinear associations.

3. Detailed Learning Objectives (con’t) 6. Identify verbs that signal causal claims versus association claims. 7. Understand the three criteria that are used to evaluate a causal claim: covariance, temporal precedence, and internal validity. 8. Understand that writers’ and researchers’ claims may not always be justified by the studies they are describing. 9. Appreciate that few studies can achieve all four kinds of validity at once, so researchers must prioritize some validities over others.

4. Variables

5. Variables Measured versus manipulated variables From conceptual variable to operational definition

7. Three Claims

8. Three Claims • Frequency claims • Association claims (types of associations) • Causal claims

11. Identifying Claims: Learning Actively #2 Fasting may fend off jet lag. Reliving trauma may help ward off PTSD. Long-term 9/11 stress found in Manhattan. Want a higher GPA? Go to a private college. Those with ADHD do one month’s less work a year. When moms criticize, dads back off baby care. Troubling rise in underweight babies in United States. MMR shot does not cause autism, large study says. Breastfeeding may boost children’s IQ. Breastfeeding rates hit new high in United States. Heavy kids may face heart risks as they age. OMG! Texting and IM-ing doesn’t affect spelling! Facebook users get worse grades in college.

12. Learning Actively #2 Indicate if the claim is frequency, association, or cause. For each claim, identify the variable(s). For each variable, is it manipulated or measured? State each variable at the conceptual level. State each variable at the operational level—how might it have been operationalized?

13. Association Claims: Types of Associations Draw a scatterplot for each of the following claims: • Facebook users get worse grades in college. • OMG! Texting and IM-ing doesn’t affect spelling! • Mother’s heartburn means a hairy newborn. What kind of association is the one you drew? (positive, negative, zero?)

14. Association and Prediction

15. Interrogating the Three Claims Using the Four Big Validities

16. Interrogating the Three Claims Using the Four Big Validities Interrogating frequency claims Interrogating association claims Interrogating causal claims

19. Interrogating Frequency Claims Construct validity of the variable How well was the variable measured? External validity is essential! Can we generalize from the sample to the population?

20. Interrogating Association Claims Construct validity of each variable How well was each variable measured? Statistical validity How strong is the association? Is it significant? External validity To whom or what can we generalize the association? May be less important to the researcher.

21. Interrogating Causal Claims Construct validity of the two variables How well was the independent variable manipulated? How well was the dependent variable measured? Statistical validity How big is the difference? How big is the effect? External validity To whom or what can we generalize this effect? External validity is rarely prioritized in an experiment Internal validity This is the priority!

22. Three Rules for Causation Covariance Temporal precedence Internal validity

23. A. Eat your broccoli. It might help your breasts. Women with diets rich in vegetables, fruit, and legumes may have a somewhat decreased risk of developing one type of breast cancer, a new study suggests. The findings, from a large, long-running study of U.S. nurses, showed that women with diets high in plant foods—but low in red meat, sodium, and processed carbohydrates—tended to have a lower risk of developing certain breast tumors. B. Day care helps kids with depressed moms The new study followed 438 Australian mothers and their children from infancy until the kids were 5 years old. Overall, children raised by mothers who reported recurrent bouts of depression were almost four times as likely to exhibit behavior problems, including depression, anxiety, withdrawn behavior, and aggression. But, as researchers reported in Pediatrics, half a day in day care significantly reduced the risk of these behavior problems developing by age 5. C. Facebook can boost self-esteem In the study, 63 Cornell students were left alone in the university's social media lab; they were seated either at computers that showed their Facebook profiles or at computers that were turned off. Some of the off computers had a mirror propped against the screen; others had no mirror. Those on Facebook were allowed to spend three minutes on the page, exploring only their own profiles and associated tabs. They were then given a questionnaire designed to measure their self-esteem.

24. Three Claims, Four Validities Find examples of each kind of claim in your headlines. Write down a question to ask of the study, or of the journalist, for each of the appropriate validities. If you think a validity is not relevant, explain why not.

25. Three claims, four validities matrix Three Claims, Four Validities

27. “That study’s just not valid!” Prioritizing Validities Which validity is appropriate to interrogate for every study? Which validities are not always relevant for a study? Why can’t researchers achieve all four validities in a single study ? Which two validities are most often in trade-off? Which validity is most under the researcher’s control?

28. Say this: Not that: How’s the construct validity? The question is, is the study valid? Is external validity relevant here? That is not a valid study. Can the study support a causal claim?