# Displaying Categorical Data - PowerPoint PPT Presentation

PPT – Displaying Categorical Data PowerPoint presentation | free to download - id: 7b52d8-MDBmM

The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
Title:

## Displaying Categorical Data

Description:

### ... (for categorical data) are bar charts and pie charts. ... Contingency Tables. ... Know the difference between a qualitative and quantitative variable. – PowerPoint PPT presentation

Number of Views:31
Avg rating:3.0/5.0
Slides: 27
Provided by: pbwo916
Category:
Tags:
Transcript and Presenter's Notes

Title: Displaying Categorical Data

1
Displaying Categorical Data
• Chapter 3

2
Data and Dirty Laundry
• Laundry needs to be separated into loads for a
machine to handle it.
• Laundry should be sorted by color (and other
factors potentially) for best results.
• Data likewise needs to be organized into
manageably small clusters or portions.
• Data likewise needs to be sorted in some
specific, useful way for best results.

3
Where to Start When Analyzing Data
• Step 1 Draw a picture.
• Humans are a visual species, and by seeing the
data we are better able to think about it.
• Step 2 Draw a picture.
• With a properly selected picture, we are better
able to demonstrate our reasoning and our
process.
• Step 3 Draw a picture.
• Once a conclusion has been reached it is often
best expressed as a picture.
• Note On some problems step 1, 2, and 3 might
each require their own pictures.

4
Frequency Vocabulary
• Frequency The number of times a value occurred.
• Relative Frequency The number of times a value
occurred divided by the total number of cases
collected.
• Often expressed as a percent.
• Frequency Table A table that displays
frequencies.
• Relative Frequency Table A table that displays
relative frequencies.

5
Step 1 Draw a Picture
frequency chart.
• Your book gave you some examples, but we will use
some hypothetical favorite color data.

6
Step 1 Draw a Picture
Color Frequency
Black 2
Blue 20
Green 14
Pink 8
Purple 5
Red 5
Yellow 6
Color Frequency
Blue 20
Green 14
Pink 8
Yellow 6
Purple 5
Red 5
Black 2
Vs.
7
Frequency vs. Relative Frequency
• With a small data set like 60, these raw counts
are not a problem.
• If you had a data set where 1472 people
contributed a favorite color, you would generally
be better off getting the relative frequency.

8
Frequency vs. Relative Frequency
Color Frequency
Blue 20
Green 14
Pink 8
Yellow 6
Purple 5
Red 5
Black 2
Color Frequency
Blue 33.3
Green 23.3
Pink 13.3
Yellow 10
Purple 8.3
Red 8.3
Black 3.3
Vs.
9
Step 2 Draw a Picture
• If all you are doing is describing the data, then
a frequency table or relative frequency table
will cover steps 1 and 2.
• The same picture that helps you think about what
is going on also helps to show what is going on.
• We will come back to what happens when you are
doing more than just describing data.

10
Step 3 Draw a Picture
• Even if you are describing the data with a
frequency chart to show what is going on, you
should use an additional picture to showcase your
findings.
• Two popular choices (for categorical data) are
bar charts and pie charts.
• Bar charts are best when the categories can be
put in some sensible order, such as months.
• They can basically always be used
• Pie charts are best when the categories do not
have a natural order, such as colors.
up to 100 of the data

11
Bar Charts and Pie Charts
• Bar charts are super crazy easy on Excel once you
get the hang of it.
• Pie charts are also easy.
• Creating a pie chart by hand is much trickier
than a bar chart, so if you are having to work by
hand you might do a bar chart instead of a pie
chart.

12
Step 1 Draw a Picture
• When we want to look at the relationship between
two variables, we will use a contingency table
• A contingency table is a table where the rows are
categories for one variable and where the columns
are categories for the other variable.

13
Contingency Table
• Once we have determined the columns and the rows,
we fill the table with the frequencies.
• Each value represents the frequency of the
category for that row happening at the same time
as the category for that column.

14
Contingency Table
• Next we will total each row and total each
column.
• Then we will total the whole table.
• To do this we total the row totals and total the
column totals to make sure they match.

15
Contingency Tables
• Relative values get trickier.
• In a frequency table, there is only one total.
• In a contingency table there is a row total and a
column total and a table total.

16
Example Time!
• If you missed class today, this was the really
• You should get notes from someone who was here.

17
Assignments
• Read Chapter 3 for tomorrow if you havent
• The Chapter 1-3 Quiz will be Friday.
• Chapter 3 5, 9, 19 (This is the first half,
more will be added before a due date is set)
• Chapter 2 homework is due tomorrow.
• Problems 2-7, 25, 26
• I will not be actively lecturing over the Area
it, you should bring those tomorrow so that when
Principle? you have a good answer.
• I will not answer the question, What even is the
Area Principle?
• Nor will I answer any of its ilk.

18
More Unsupporting Cast
• On yesterdays episode we talked about Mr.
Cheeseburger and then need for ridiculously
levels of clarity.
• Today we will focus on the Casual Observer, the
Hasty Generalizer and the Exemplar, which might
seem like the same at first, but are actually
three very differently flawed archetypes.
• They do, however, have in common that they come
to their conclusions far too easily.

19
The Casual Observer
• This phrase normally refers to a person who is
looking at the situation, but does not have any
particularly strong background in what is going
on and who does not look any deeper than what is
on the surface.
• We are using it to refer to someone who does
exactly that with exactly the same restrictions.
• Casual Observers are easily swayed by misleading
pictures and misinformation because they are only
looking at what is immediately available.

20
The Casual Observer
• The reason it is important to be aware of these
observers is that the reason we must be concise
is because if we take yawn-worthy lengths of time
to get to our true point, some people will have
totally tapped out by then.
• We need to get to our points in a timely manner
so that a casual observer gets the information
before they would otherwise give up.

21
The Hasty Generalizer
• A hasty generalization is when a person assumes
that something which is/seems true in some
situation is also actually true in many, if not
all, similar situations.
• The person I refer to here is a little different
than that, though.
• In this context I am referring to a person who
just wants you to get to the conveniently
digested point, not really caring how you got
there, so they can get on with their day.

22
The Hasty Generalizer
• Such a person will typically latch on the first
solid point you make and assume that the rest of
what you said is meaningless, unless a better
point comes along.
• At which point they tend to abandon the original
point in favor of the new one.
• It is important to be complete while being
concise in order to get around this. Your entire
point needs to be visible in a relatively concise
and clear manner for someone trying to breeze
through it to get the full effect.

23
The Exemplar
• Normally an exemplar would be someone who has
done things in a way that sets a superior example
for others to follow.
• In this case, though, I am referring to a person
who fixates on a specific example of something
happening, and assumes that it is way more
important than it is.
• Interestingly enough, that is actually closer to
a hasty generalization, most of the time, than it
is to anything else.

24
The Exemplar
• For example, this person assumes that 9 out of
10 dentists approving of a particular dental
product means that 1 of them did notand that it
should be closely investigated as to exactly why.
• This kind of person also assumes that there is
genuine scientific controversy as to the
existence of global warming because there are
scientists which are unconvinced.
• This kind of person might get pulled over once
for running a stop sign and then immediately
decides that cops will always pull you over for
running stop signs.

25
The Exemplar
• This sort of person tends to believe that one
rather unlikely example should hold just as much
weight as the ongoing, consistent outcomewhich
is the opposite of that example.
• It is very important that we address any and all
unusual results in our efforts to avoid someone
taking them and running with them,
metaphorically, which means taking time to
explore possible reasons that strange results
occurred.

26
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.