The Exciting Conclusion!

1
The Exciting Conclusion!

• of Chapter 3

2
Segmented Bar Charts

• A segmented bar chart is a bar chart where each
  variable is stacked on top of the other.
• While technically called a bar chart, it is
  basically a pie chart in the shape of a stick.

3
Pie On A Stick Is Real!
4
Segmented Bar Chart

• Here is our color data

5
Marginal and Conditional

• If we isolate the row totals or the column totals
  of a contingency table, we call it a marginal
  distribution.
• If we isolate a specific row or a specific column
  along with the relative frequencies, this is
  called a conditional distribution.

6
Independence

• We will talk more about this later.
• For now, just know it means the two variables do
  not interact in a special way.
• You can also think of it as the two variables not
  having any influence on one another.

7
Simpsons Paradox

• Sometimes when we have two variables, they work
  together in a way that hides what is really going
  on.
• Looking only at overall averages might disguise
  the effect of the interaction.

8
From The Book

• On page 33 of the book, a good example is given.
• Moe and Jill are pilots who are trying to see who
  is the better pilot at landing flights on time.
• Moe has landed 83 of his last 120 flights on
  time.
• Jill has landed 78 of her last 120 flights on
  time.

9
From The Book

• Jill is the better pilot for landing flights on
  time.
• Her 78 is misleading, because it assumes that
  all flights are created equal.
• It turns out to matter whether the flight is
  during the day or at night.

10
Step 1 Draw a Picture

• We will look at the rates for nighttime and
  daytime flights.

Time of Day of Flights Landed On Time
Daytime 90.8
Nighttime 70.8
11
Step 1 - Think

• It would seem that clearly the 20 difference
  between nighttime and daytime flight rates could
  matter.
• Our data should be arranged in a way that shows
  what is really going on.

12
Step 2 Draw a Picture
Day Night Overall
Moe 90 of 100 90 10 of 20 50 100 of 120 83
Jill 19 of 20 95 75 of 100 75 94 of 120 78

• As we can see here, Jill is the better pilot in
  the day and
• the better pilot at night

13
Step 3 Draw a Picture

• The picture from step 2 is good for the telling
  step as well.
• We would want to formally say, Since Jill is a
  better pilot at night and during the day, she is
  the better pilot overall.
• In case we do not expect to be believed, we could
  point out that Jill flies more nighttime flights
  which is why her average is lower.

14
Assignments

• Chapter 3 HW 5, 9, 19, 25, 33, 37
• Due some time next week. Wednesday at the
  earliest.
• Dont forget to turn in chapter 2 HW.
• Read chapter 4 through page 50 for Monday.
• Chapter 1-3 Quiz Tomorrow!
• Yay!

15
More Unsupporting Cast

• Now we will focus on three more members of our
  unsupporting cast.
• We will talk about the Scientist and we will
  talk about the Cave Person, and the Disbeliever.
• These are differently flawed archetypes, but what
  they have in common is that they tend to hold to
  awkward belief systems.

16
The Scientist

• In case you did not know, a proper scientist
  places their allegiance in the scientific method.
• One of the most wonderful things about the
  scientific method is that it only establishes
  that information is apparently correct, and is
  theoretically open to the idea that if it ever
  gets disproven, that a new theory would be needed.

17
The Scientist

• Science is, therefore, inherently open-minded.
• Science can also refer to the body of current
  scientific knowledge.
• Which I cannot stress enough is only true until
  proven otherwise.
• The methods of science are sensible and logical
  and things which are found through science tend
  to be reliably true.

18
The Scientist

• Some people, though, treat science like it is
  dogma.
• This means that they treat it like because
  science said so, it is always true forever.
• Like a Crusaders motto of God wills it! they
  favor a Science proves it! approach.
• Instead of being open to alternative viewpoints
  having merit, they will defend their awareness of
  scienceto the death.

19
The Scientist

• Studies, and even science, do not prove anything.
• They support ideas with various degrees of
  evidence, ranging from sketchy to overwhelming.
• Be careful not to overgeneralize what the results
  of a study mean and avoiding confusing scientific
  knowledge with religious dogma.

20
The Cave Person

• Some people believe that tradition is more
  important than truth.
• The fact that things used to work a certain way
  means they should continue to work that way.
• But we have progressed past the stone age and
  civilization continues to march forward.
• If you ever decide you have learned enough about
  a topic, you risk being this unevolved
  culturally.
• In order to avoid this, we need to be open to the
  idea that the entire world around us could be
  different than we thoughtand that we should be
  the ones to change to fix the discrepancy.

21
The Disbeliever

• Some people believe that everything people tend
  to say is an obvious lie if it is disagrees with
  how they feel.
• They will demand proof.
• Then, in the face of proof, they will demand
  better proof.
• Then, in the face of better proof, they will
  still possibly not believe you because everything
  can be photoshopped.
• It is best to avoid holding to this sort of a
  mentality in the face of strong proof. You do
  not even have to assume that proof changes
  everything all the time, but it helps to be aware
  of the simple idea that some things are true even
  if you disagree.

22
Quiz Bulletpoints

• Know what T-S-T stands for and what each one
  means.
• Know how to identify the 5 Ws and How in a
  study.
• Know the difference between a qualitative and
  quantitative variable.
• Know how to find percentages from a contingency
  table.
• Know the area principle.