____ variable and generosity is the ______ variable. • A. Confounding, dependentB. Dependent, confoundingC. Dependent, independentD. Independent, dependent • • •
Three Claims • Claim: the argument that someone is trying to make or proposition that someone asserts – EX: Music lessons can raise a child’s IQ
Three Claims • Frequency and intensity claims • Association claims • Causal claims
• “40% of Americans took an antidepressant in 2013” • Gives percentage or mean of some “event” in population (Americans exercise .75 times a week) • Focus on only one variable (% of Americans taking meds) • Variable ALWAYS measured, never manipulated
“Income is inversely related to heart disease” • X and Y are related • As x changes, so does Y • Does not claim that X causes Y! • Claim allows vbls being related for any reason • Two measured (not manipulated) variables
Four Types of Associations: – Positive – Negative ( r = .35) ( r = -.35) % abdominal fat min/day on phone Level of dementia age 60 Written pages/day
Four Types of Associations: Curved Relationship ( r = 0) No relationship ( r = 0) Duration of Use ADHD Drugs Frequency of adult drug use 50100150200250 H o rsepow e r 10 20 30 40 50 M iles p e r G a llon R S q L inea r = 0 .595 r is misleading
What type of relationship is this (+,0,-)? – Facebook users get worse grades in college. – OMG! Texting and IM-ing doesn’t affect spelling! – Mother’s heartburn means a hairy newborn.
• “Music lessons can increase a child’s IQ” • Has two variables and the variables covary (related) • As x changes, so does Y, AND • X is responsible for changes in Y (necessary and sufficient; not necessarily sole cause, except in the study) • Can be probabilistic, e.g., drug effectiveness
Identifying Claims in the Media: frequency, association, or cause? [A=freq,B=assoc,C=cause] a. Fasting may fend off jet lag. (Cause) b. People in large families less likely to show PTSD. (Associate) c. Long-term 9/11 stress found in Manhattan. (Freq) d. Want a higher GPA? Go to a private college. e. ADHD workers predicted to be less productive . f. When moms criticize, dads back off baby care. g. Troubling rise in underweight babies in US. h. MMR shot does not cause autism, large study says . i. Breastfeeding boosts children’s IQ. (Cause) j. Breastfeeding rates hit new high in United States . k. Heavy kids read more books.
Researcher’s Claim • The purpose or inference (claim) that you want to make determines what the IV, DV and confounding variables are. • Alcohol consumption can be an IV, DV or confounding variable . – Drinking (IV) leads to poor decision making (DV) – Negative affect (IV) leads to drinking (DV) – Anger management (or how to win friends at a bar) compared to control group (IV) on outbursts (DV) – drinking as confound, e.g., reason for enrolling if not assigned to group
Research Design • In an experimental study, the participants are ASSIGNED to conditions or treatments, that is, they are assigned to the levels of the IV. The IV can be nominal (categories) or continuous.
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- Fall '08
- Causality, external validity, internal validity, Confounding, Statistical terminology