5. Different types of counting
• Numeric
o Continuous or discrete
o Units of measurement?
o Non-linear scales?
• Categorical
o finite, e.g. {true, false}
o infinite e.g. {red, yellow, blue, ... chartreuse…}
o ordered?
14. Some things that are tricky to quantify,
but usefully quantified anyway
• Intelligence
• Academic performance
• Race, ethnicity, nationality, gender
• Number of incidents of some type
• Income
• Political Ideology
17. It looks like Lucknow and Kanpur have few traffic accidents, but
deaths data suggests that accidents are not being counted.
Lies and Statistics: How India’s Most-Populous State Fudges Crime Data, IndiaSpend
18. Evaluating Data Quality
Internal validity: check the data against itself
• row counts (e.g. all 50 states?)
• related data
• histograms
• do the numbers add up?
External validity: compare the data to something else.
• alternate data sources
• expert knowledge
• previous versions
• common sense!
19. Interview the Data
• Who created this data?
• What is this data supposed to count?
• How was this data actually collected?
• Does it really count what it’s suppose to?
• For what purpose was this data collected?
• How do we know it is complete?
• If the data was collected from people, who was asked
and how?
20. • Who is going to look bad or lose money because of this
data?
• Is the data consistent with other sources?
• Is the data consistent from day to day, or when collected
by different people?
• Who has already analyzed it?
• Are there multiple versions?
• Does this data have known problems?
Interview the Data
23. AP Clinton Foundation Story
WASHINGTON (AP) — More than half the people outside the government who
met with Hillary Clinton while she was secretary of state gave money — either
personally or through companies or groups — to the Clinton Foundation. It’s an
extraordinary proportion indicating her possible ethics challenges if elected
president.
At least 85 of 154 people from private interests who met or had phone
conversations scheduled with Clinton while she led the State Department
donated to her family charity or pledged commitments to its international
programs, according to a review of State Department calendars released so far
to The Associated Press. Combined, the 85 donors contributed as much as
$156 million. At least 40 donated more than $100,000 each, and 20 gave more
than $1 million.
- Many donors to Clinton Foundation met with her at State, AP, 8/24/2016
26. AP Clinton Foundation Story
“At least 85 of 154 people from private interests who met or had phone
conversations scheduled with Clinton while she led the State Department
donated to her family charity or pledged commitments to its international
programs, according to a review of State Department calendars.”
odds
27. AP Clinton Foundation Story
odds
Not enough information to compute the odds ratio...
which you can tell immediately because four values are required.
43. How correlation happens
YX
X causes Y
YX
Y causes X
YX
random chance!
YX
hidden variable causes X and Y
YX
Z causes X and Y
Z
44. Guns and firearm homicides?
YX
if you have a gun, you're going to use it
YX
if it's a dangerous neighborhood, you'll buy a gun
YX
the correlation is due to chance
45.
46. Beauty and responses
YX
telling a woman she's beautiful
makes her respond less
YX
if a woman is beautiful,
1) she'll respond less
2) people will tell her that
Z
Beauty is a "confounding variable." The correlation is real,
but you've misunderstood the causal structure.
