Transcript A Primer for the Need to Learn Statistics

Something that will (hopefully) make you
want to learn about probability & statistics
2
(for reasons greater than “my degree says I have to”)
Part I: Fact Check!
2006 – CBS reports that an appalling number of food
poisonings happened in US school cafeterias in 2005...
733
How horrid! But...
According to the CDC, there are 76 million food
poisonings per year in the US.
Assuming 300 million Americans eating, on average,
3 meals per day, the rate of food poisoning in America
is about
76, 000, 000
 0.0002, or 0.02%.
300, 000, 000  3  365
2006 – CBS reports that an appalling number of food
poisonings happened in US school cafeterias in 2005...
733
According to the US Census Bureau, there were
approximately 75,800,000 children in school in 2005.
Thus, the rate of food poisoning in school cafeterias was
733
 0.00000005, or 0.000005%.
75,800, 000 180
...or, about 4000 times less likely than the general population.
100 species on earth become extinct every day.
COCC blocks roughly 50,000 Spam emails a day.
As of 2011, there are 550 million people using Facebook . In the
time it took you to read that last sentence, they uploaded 5000 photos.
1 billion people worldwide watched the 2006 World Cup Final.
 In the first half of 2008, American drivers logged 30 billion
fewer miles than in the first half of 2007.
 The US uses almost a quarter of a trillion plastic beverage bottles
each year.
 The US has a national debt of just over 14 trillion dollars (as of
2011). By the time you finish reading this sentence, it will have
grown by about $100,000.
(sources: World Resource Institute, Wade DeBral, TIME, Mark Zuckerberg, FIFA, CNN, Chris
Jordan, Congressional Budget Office)
Part II: Read deeply...
and look carefully!
Anything wrong with this graph?
1600
Tuition
1400
($)
1200
Cost of Tuition Analysis
old tuition
new tuition
1000
800
600
400
200
0
8 credits
12 credits
16 credits
20 credits
Part III: Correlation does
not imply Causation!
Fact: Ice-cream sales are strongly correlated with crime rates.
Possible Conclusion: Therefore, higher ice-cream sales cause
crime.
Alternate Conclusion: High temperatures increase icecream sales but also increase crime rates - perhaps by
making people irritable or restless, or by increasing the
number of people outside at night.
Historically, parents of daughters are more likely to
divorce than parents of sons. If you have daughters, should you
worry about divorce?
What could justify this correlation?
Possible Conclusion: In many species, stressed populations
produce disproportionate numbers of female offspring (Why? I
don’t know). Perhaps the stress came first, followed by the
daughters (instead of the daughters first, then the divorce).
Apparently, it’s a lot of work to insert testosterone!
Part IV: How Random!
Randomness in 30 darts thrown...spot the fake!
Don’t buy it?
Randomness in 200 flips of a coin...spot the fake!
Sequence #1
HTHHHHHTTHHHHTTHTTHHTHTHTHHTTTHTHTTHHHHHTHHTHHTHTTHTHHHHHHTTH
HTTHHTTTHHTHHTHTHTHTTHHTTHHTTHHTHTTTTTHTHHTTHTTHTHTHTHHHTHHTTTH
HTTHHHTTTTHHTHHTTHTTTTHHHHTTTHTHHTTTTTHTTHHHHHTHTTTHHTHTHHTHTHH
HTTTHTHHTHTHT
Sequence #2
HHTTTHTTHHHTHHHTHHTTHHHTHTTTHTTTHHTTTHHTHTTHHTTHHHTHTTTHHTTHTTT
HHTHHHTTTHHHTTHTTHHHTHTTTHHHTTHHTHTHTTTHHTHHHTTTHTHTHHTHTTTHHT
HHHTHHHTTHHTTTHHTHTTHHHTTHHTTHHTTTHTHTTTHHHTTHTHHTTHTTHHHTTTHTT
HHHTTTHTHTTT
Chance of at least a run of 6 in 200 flips  96%
Don’t buy it?...and what does this have to with my birthday?