# Lock1-3 - Section 1.3 Experiments and Observational Studies...

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Statistics: Unlocking the Power of Data Lock 5 Section 1.3 Experiments and Observational Studies
Statistics: Unlocking the Power of Data Lock 5 Outline Association versus Causation Confounding Variables Observational Studies vs Experiments Randomized Experiments
Statistics: Unlocking the Power of Data Lock 5 Mini Review Quiz To 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 is a) Not biased b) Biased because of wording bias c) Biased because asked over email instead of in person d) Biased because responses may be inaccurate e) Biased because volunteer samples are almost always biased
Statistics: Unlocking the Power of Data Lock 5 DATA Data Collection and Bias Population Sample TODAY
Statistics: Unlocking the Power of Data Lock 5 Association 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
Statistics: Unlocking the Power of Data Lock 5 Explanatory, Response, Causation For each of the following headlines: Identify the explanatory and response variables (if appropriate). Does the headline imply a causal association? 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 Lock 5 College 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, 1/19/12 People who go to college may be different to begin with!
Statistics: Unlocking the Power of Data Lock 5 0 200 400 600 800 1000 40 50 60 70 80 TVs per 1000 People Life Expectancy Angola Australia Cambodia Canada China Egypt France Haiti Iraq Japan Madagascar Mexico Morocco Pakistan Russia South Africa Sri Lanka Uganda United Kingdom United States Vietnam Yemen r = 0.74 TVs and Life Expectancy Should you buy more TVs to live longer? Association does not imply causation!
Statistics: Unlocking the Power of Data Lock 5 Confounding Variable A 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