Detailed Learning Objectives1. 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.

Detailed Learning Objectives (cont)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.

Variables

VariablesMeasured versus manipulated variablesFrom conceptual variable to operational definition

Three Claims

Three ClaimsFrequency claimsAssociation claims(types of associations)Causal claims

Identifying Claims: Learning Actively #2Fasting 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 months 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 childrens IQ.Breastfeeding rates hit new high in United States.Heavy kids may face heart risks as they age.OMG! Texting and IM-ing doesnt affect spelling!Facebook users get worse grades in college.

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 levelhow might it have been operationalized?

Association Claims: Types of AssociationsDraw a scatterplot for each of the following claims:Facebook users get worse grades in college.OMG! Texting and IM-ing doesnt affect spelling!Mothers heartburn means a hairy newborn. What kind of association is the one you drew? (positive, negative, zero?)

Association and Prediction

Interrogating the Three Claims Using the Four Big Validities

Interrogating the Three Claims Using the Four Big ValiditiesInterrogating frequency claimsInterrogating association claimsInterrogating causal claims

Interrogating Frequency ClaimsConstruct validity of the variableHow well was the variable measured?External validity is essential!Can we generalize from the sample to the population?

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

Interrogating Causal ClaimsConstruct validity of the two variablesHow well was the independent variable manipulated?How well was the dependent variable measured? Statistical validityHow big is the difference? How big is the effect?External validityTo whom or what can we generalize this effect?External validity is rarely prioritized in an experimentInternal validityThis is the priority!

Three Rules for CausationCovarianceTemporal precedenceInternal validity

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 foodsbut low in red meat, sodium, and processed carbohydratestended to have a lower risk of developing certain breast tumors.B. Day care helps kids with depressed momsThe 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-esteemIn 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.

Three Claims, Four ValiditiesFind 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.

Three Claims, Four ValiditiesThree claims, four validities matrix

FrequencyAssociationCausalConstructStatistical

InternalExternal

Prioritizing ValiditiesWhich validity is appropriate to interrogate for every study? Which validities are not always relevant for a study? Why cant researchers achieve all four validities in a single study ? Which two validities are most often in trade-off? Which validity is most under the researchers control?That studys just not valid!

The question is, is the study valid? That is not a valid study. Say this: Not that: Hows the construct validity? Is external validity relevant here?Can the study supporta causal claim?

******

********Source for first example (notably, MSNBC has changed the causal headline since I found this example!):http://www.msnbc.msn.com/id/44426450/ns/health-cancer/t/plant-rich-diets-tied-lower-breast-cancer-risk/

Source for second example:http://health.usnews.com/health-news/family-health/brain-and-behavior/articles/2011/06/13/child-care-can-help-kids-with-depressed-moms

Source for third example:http://www.webmd.com/balance/news/20110304/facebook-boosts-self-esteem

*****