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12/23/2012 1 Statistics: Unlocking the Power of Data Lock5STAT 101 Dr. Kari Lock Morgan 9/4/12 Collecting Data: Experiments SECTION 1.3 •Association versus Causation •Confounding Variables •Observational Studies vs Experiments •Randomized Experiments Statistics: Unlocking the Power of Data Lock5-use-causes-mental-deficit Statistics: Unlocking the Power of Data Lock5Statistics: Unlocking the Power of Data Lock5DATA Data Collection and Bias Population Sample TODAY Statistics: Unlocking the Power of Data Lock5Explanatory and Response If we are using one variable to help us understand or predict values of another variable, we call the former the explanatory variableand the latter the response variableExamples: Does meditation help reduce stress? Does sugar consumption increase hyperactivity? Statistics: Unlocking the Power of Data Lock5Association and Causation Two variables are associated if values of one variable tend to be related to values of the other variable Two variables are causally associated if changing the value of the explanatory variable influences the value of the response variable
12/23/2012 2 Statistics: Unlocking the Power of Data Lock5Explanatory, Response, Causation For each of the following headlines: Identify the explanatory and response variables (if appropriate). Does the headline imply a causalassociation? 1.“Daily Exercise Improves Mental Performance”2.“Want to lose weight? Eat more fiber!”3.“Cat owners tend to be more educated than dog owners”Statistics: Unlocking the Power of Data Lock5Association and Causation ASSOCIATION IS NOT NECESSARILY CAUSAL! Come up with two variables that are associated, but not causally Come up with two variables that are causally associated Which is the explanatory variable? Which is the response variable? Statistics: Unlocking the Power of Data Lock5College Education and Aging “Education seems to be an elixir that can bring us a healthy body and mind throughout adulthood and even a longer life,” says Margie E. Lachman, a psychologist at Brandeis University who specializes in aging. For those in midlife and beyond, a college degree appears to slow the brain’s aging process by up to a decade, adding a new twist to the cost-benefit analysis of higher education —for young students as well as those thinking about returning to school.”Are you convinced that a college degree slows the brain’s aging?a)Yes b)No People who go to college may have better brains to begin with! A Sharper Mind, Middle Age and Beyond -NY Times, 1/19/12 Statistics: Unlocking the Power of Data Lock5020040060080010004050607080TVs per 1000 PeopleLife ExpectancyAngolaAustraliaCambodiaCanadaChinaEgyptFranceHaitiIraqJapanMadagascarMexicoMoroccoPakistanRussiaSouth AfricaSri LankaUgandaUnited KingdomUnited StatesVietnamYemenr = 0.74TVs and Life Expectancy Should you buy more TVs to live longer?