




Pros: Visually
appealing
Shows percent of total
for each category
Cons: No exact
numerical data
Hard to compare 2
data sets
"Other" category can
be a problem
Pros: quickly compare
different categories
 Easier to make and
read.
 Visually strong


Cons: Graph categories
can be reordered to
emphasize certain
effects
How is this
graph
misleading??
Which one
could be
considered
deceptive??
Why??

Graphs of Quantitative Data
Dotplot


Stemplot
Histogram
Individual:
Variable:
Distribution of a Variable:
Outlier:
Use SOCS to describe
the overall pattern of
a distribution.
Shape: Symmetric, Skewness, Unimodal,
Bimodal, Multimodal
Outliers: Visually or using (IQR) Interquartile
Range
Center: Visually or mean/median
Spread: Min to max with range
Symmetric distribution:
Symmetric Distribution:
Skewed to the right:
Skewed to the right:
Skewed to the Right:
Skewed
Skewed toto
thethe
left:left:
Skewed to the Left:
You are always skew
Always skewed in the _________________________!!!
You are always s
Dotplot: a quick way to visualize
a set of data.
The digit(s) in the greatest place value(s) of the data
values are the stems. The digits in the next greatest
are the leaves.
Example: Consider the scores for Test 1 for the class
of 25 students:
75, 8, 36, 36, 55, 55, 27, 83, 17, 58, 55, 42, 36, 50,
42, 82, 27, 92, 50, 42, 100, 83, 27, 58, 55
Split Stem: each stem is listed
more than once
Example: Number of touchdown passes.
47, 33, 33, 32, 29, 28, 28, 23, 22, 22, 22, 21,
21, 21, 20, 20, 19, 19, 18, 18, 18, 18, 16, 15,
14, 14, 14, 12, 12, 9 ,6
Back to Back Stem Plot: Two sets of data can be compared using a b
BacktotoBack
Back
Stem
Plot: Twostem-and-leaf
sets of data can
be
compared
usingscor
a ba
stem-and
leaf
plot.
The back-to-back
plot
below
shows
Back
Stem
Plot: Two sets
of data can be
compared
using athe
back-to
stem-and leaf
plot.
back-to-back
below shows the score
basketball
teams
forThe
the
games in stem-and-leaf
onestem-and-leaf
season. plot plot
tem-and leaf
plot. The
back-to-back
below shows the scores of t
basketball teams for the games in one season.
asketball teams for the games in one season.
Histograms
Histograms
Histograms
Determine
the
number
of classes
- usually
you you
will have
from from
5 to 8;5itto
Determine
the
number
of
-- usually
will have
have
8;ititde
de
Determine
the
number
of classes
classes
usually
you
will
from
5 todepends
8;
many
values
you
have
andand
thethe
spread
of the
manydata
data
values
you
have
spread
ofdata.
the data.
many data values you have and the spread of the data.
Frequency Table:

breaks the range of values of a variable into
intervals and displays only the count or percent of
the observations that fall into each interval
1.
Divide the data into classes (intervals) of equal width.
- Need to specify the classes so that each individual falls
into one class.
- Usually will need between 5 to 8 intervals
2.
Find the count (frequency) or percent (relative
frequency) of individuals in each class.
- Do this by making a frequency or relative frequency
table.
3.
Label and scale your axes
4.
Draw the histogram
Consider the following data on the Survey of
Study Habits and Attitudes (SSHA) scores for 18
female college students. The test evaluates
motivation, study habits, and attitudes toward
school. Make a histogram and interpret the
SOCS of the data.