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Statistics: Unlocking the Power of DataLock5Section 1.3Experiments and Observational Studies
Statistics: Unlocking the Power of DataLock5OutlineAssociation versus CausationConfounding VariablesObservational Studies vs ExperimentsRandomized Experiments
Statistics: Unlocking the Power of DataLock5Mini Review QuizTo estimate the proportion of students who support a smoke-free campus, you compute the proportion that say yes after responding to an email sent to all students asking “Do you support a smoke-free campus?” The data collected isa)Not biasedb)Biased because of wording biasc)Biased because asked over email instead of in persond)Biased because responses may be inaccuratee)Biased because volunteer samples are almost always biased
Statistics: Unlocking the Power of DataLock5DATAData Collection and BiasPopulationSampleTODAY
Statistics: Unlocking the Power of DataLock5Association and CausationTwo variables are associated if values of one variable tend to be related to values of the other variableTwo variables are causally associated if changing the value of the explanatory variable influences the value of the response variable
Statistics: Unlocking the Power of DataLock5Explanatory, Response, CausationFor 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 DataLock5College 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 education slows the brain’s aging?A Sharper Mind, Middle Age and Beyond-NY Times, 1/19/12People who go to college may be different to begin with!
Statistics: Unlocking the Power of DataLock5020040060080010004050607080TVs per 1000 PeopleLife ExpectancyAngolaAustraliaCambodiaCanadaChinaEgyptFranceHaitiIraqJapanMadagascarMexicoMoroccoPakistanRussiaSouth AfricaSri LankaUgandaUnited KingdomUnited StatesVietnamYemenr = 0.74TVs and Life ExpectancyShould you buy more TVs to live longer?Association does not imply causation!
Statistics: Unlocking the Power of DataLock5Confounding VariableA third variable that is associated with both the explanatory variable and the response variable is called a confounding variable•A confounding variable can offer a plausible explanation for an association between the