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STARBUCKS OBSERVATIONAL
STUDYAnalyze the Data
Present Task: Analyze the Data
What did we learn from the data? Does this sample convince you that more than
half of all customers at this store are female? What do you think the real percentage is? 60%,
70%, 80%? What values are a reasonable guess for the
population of females? What percentage was of females was present for
our sample? Does our sample proportion convince you that
more than half of all the customers at this Starbucks are female?
Dice Intervention
Roll 2 dice and add them together. What are the possible totals? Which sum will come up most often? Do these dice seem “fair”? How does this relate back to the sample
data? Lets assume the Starbucks population is
”fair” or 50-50. Is there an experiment we can conduct to determine if your sample data is acceptable?
Coin Toss Experiment
Flip your coin 26 times and record the results Can we extend this type of reasoning to our
sample of 260 customers? Is it possible that 50% of the customers were
male and 50% female and you just happened by coincidence to get more females in your sample?
How can we decide whether our sample result is different enough from 50-50 to convince us there is something funny going on?
Computer simulation
Computer Simulation
Let the computer applet toss a coin 260 times
If we get heads, that customer is a female, tails means a male
With this experiment, we can repeat the process of sampling from a 50-50 population many times (unlike the actual study)
References
Shaughnessy, M., Chance, B., and Kranendonk, H. (2009). Focus in high school mathematics: Reasoning and sense making in statistics and probability. NCTM.
Key Curriculum Press: Exploring Statistics with Fathom, 2007
Coin Toss Applets: http://
www.socr.ucla.edu/htmls/SOCR_Experiments.html
http://statweb.calpoly.edu/bchance/applets/BinomDist3/BinomDist.html