Chapter 2:
PICTURING VARIATION WITH GRAPHS
HOW MANY...

Come up to board and write the number of
different types of social media YOU have used
TODAY; write anywhere; no need to organize in
any special way.
If you are male, please use a blue marker
 If you are female, please use a black marker

HOW MANY...

Number of different types of social media YOU
have used TODAY; blue: male; black: female

One minute to talk to the person next to you
about one observation you can make about our
data; be prepared to share out your
observation
HOW MANY...

Number of different types of social media YOU
have used TODAY; blue: male; black: female

First, it’s always helpful to ...

Second, and probably more importantly, it’s
always helpful to ...
GRAPHICAL REPRESENTATIONS...
GRAPHICAL REPRESENTATIONS...

Talk to the person next to you for 2 minutes. What
type of graphical representation would you choose
to best represent this data and why (your group
doesn’t actually have to create the graphical
representation at this time). Be prepared to
explain/justify your reasoning/your choice.

Share out.
GRAPHICAL REPRESENTATIONS FOR NUMERIC
(OR QUANTITATIVE) DATA INCLUDE...
Dot plots
 Stem (and leaf) plots
 Histograms
 Box plots (later...)
 (and much later) ... Density curves, scatter plots,
least-squares regression lines, Normal probability
plots, etc.


Why didn’t I list pie charts or bar graphs?
NO MATTER WHAT...
We always want to create a graphical representation;
visuals help us process information, indentify
trends more easily
We always label & scale our graphical
representations
We always use technology when available (no need
to create graphical representations by hand)
LETS CREATE SOME GRAPHICAL
REPRESENTATIONS USING OUR CLASS DATA...

Dot plot... What’s good about dot plots? What’s
not so good?

Histogram... What’s good about histograms?
What’s not so good?

Stem (and leaf) plots... What’s good about stem
plots? What’s not so good?

Box Plots... In Minitab, but will learn much more
about box plots later...
LET’S PRACTICE ONE MORE GRAPHICAL
REPRESENTATION... PARTNER CLASS WORK

Go to my website, click on COC Math 140 Survey
Data Fall 2015 spreadsheet. Find the column
‘How much do you weigh (in pounds).’ Copy and
past into a column in Minitab.

Create a histogram, a stem plot, a dot plot, or a
box plot of this data (your choice). Be sure to label
your graphical representation. Put both your
names on it.

Print it, but do not turn it in yet; we will be doing
something else with it in a little while.
NOTE ON HISTOGRAMS...

Frequency vs. Relative Frequency
LET’S LOOK AT GRAPHICAL REPRESENTATION
OF ‘WEIGHTS’...

No matter which graphical representation you
created with this data set, how could you
describe your graphical representation?

What types of characteristics might we consider
when trying to describe the graph of this data?
SOCS...
S – Shape.
Symmetric? Skewed? Uni-Modal, bi-modal,
tri-modal, multi-modal?
O– Outlier(s)
Is/are there unusually large or small values
that are “away” from the majority of the rest
of the data?
C – Center
What is the “typical*” value of the
distribution/data?
S – Spread
Typically/on average*, how far apart or close
together is the data/distribution?
* Different types of ‘averages’ and ‘typical’. Will discuss further and in detail soon.
LET’S DESCRIBE OUR DATA USING SOCS...
Practice: Lets look at our social media data with a
histogram, dot plot, stem plot, or box plot; &
describe the distribution using SOCS
 Now with the graphical representation you and
your partner created from the ‘weights’ data,
describe the distribution using SOCS. You have 5
minutes. You will turn this in as an assignment.
 Be prepared to do a 1-minute share out as I will
randomly call on a few pairs to share out

DATA GATHERING TIME... AGAIN...

Write on the board the type of first pet you
ever had
WHAT TYPES OF GRAPHICAL REPRESENTATIONS
CAN WE USE? WHAT CAN WE NOT USE? WHY?

Type of first pet ... or favorite social media,
favorite app for cell phone, hair color, make of
car you drive, marital status, etc.
GRAPHICAL REPRESENTATIONS FOR
CATEGORICAL (QUALITATIVE) DATA...

Bar (charts) graphs (caution; very different from
histograms; why?)
CAUTION... BAR GRAPHS VS. HISTOGRAMS...
On left is bar graph; on right is histogram
 Be sure you understand the difference between
the two graphical representations

NOW BACK TO GRAPHICAL REPRESENTATIONS
FOR CATEGORICAL (QUALITATIVE) DATA...

Bar (Charts) Graphs

Pie Charts

BIG IDEA... the same... visualizing data can be helpful in
observing trends
Can we analyze pie charts or bar graphs with SOCS? Why or
why not?


Whether categorical or numerical, always good to graph your
data
LET’S GRAPH OUR DATA...

Using our ‘first pet you ever had’ data, input
into Minitab

Practice creating a bar graph AND a pie chart
using with the pet data
DECEPTION…
WATCH FOR IT…
WHAT’S WRONG?
DECEPTION…
… FIXED ... SORT OF....
DIFFERENT BIN WIDTHS IN HISTOGRAMS... NOT
A GOOD THING –VERY DECEPTIVE
MORE DECEPTION…
DECEPTION… WITH THE DATA, AND THE
GRAPHICAL REPRESENTATION…
CLASS/GROUP ACTIVITY… PAGE 58 OF
TEXTBOOK
Form groups randomly (how would we like to do
this?)
 In your group, answer the ‘Before the Activity’
questions (one paper per group; include all
names)
 Gather our data (for entire class), then write it
on board; let’s use blue marker for male; black
for female
 Input all data from class into Minitab

CLASS/GROUP ACTIVITY… PAGE 58
Do “After the Activity;” follow all directions
 1-2 paragraph write up answering questions
asked in ‘After the Activity;” also include
justification of the group’s choice of graphs
 Include the actual graphs & numerical analysis
(SOCS) of data/graphs (from Minitab)
 All members of group must contribute
 Maximum points possible: 20 project points.


HW quiz on ...