Data Collection and
Histograms
Unit 5: Statistics
Basic Statistics
Data can be divided into 2 types:
Qualitative variable- places an individual
into a group or category
ex: gender, college major, blue eyes, liberal
Quantitative variable- takes numerical data
ex: age, GPA, hours spent studying
Qualitative or Quantitative?
The height of each player on a basketball
team?
The style of shoes worn by each student in
a classroom?
The number of people in each household
in the US?
Data Displays
The number of times a value occurs is
known as the frequency of that value.
The relative frequency is the frequency
divided by the total number of responses
(written as a fraction, decimal, or %)
A frequency table displays the categories
is frequencies, relative frequencies, or
both.
Frequency Table
 A group of people
were asked their
favorite flavor of ice
cream. Of these, 6
chose vanilla, 12
chose chocolate, 4
chose butter pecan,
and 8 chose mint
chocolate chip. Create
a table with
frequencies and
relative frequencies for
each flavor.
Flavor
Vanilla
Choc
Butter
Pecan
Mint
Choc
Freq
Relative
Freq
Let’s do our own…
 Choose your favorite
color from the table
(only choose one).
Let’s create a
frequency table on
the class’s findings.
Color
Blue
Red
Yellow
Green
Freq
Relative
Freq
Displaying Data
Bar Graphs – displays the categories on
the horizontal axis and the frequency or
relative frequency on the vertical axis. The
height of each bar shows the frequency of
that value.
Displaying Data
Pie Charts –
displays the
categories and
their relative
frequencies.
All adds up to
100% - full
circle!
Common Distribution Shapes
 Uniform
 Skewed Right
 Symmetric
 Skewed Left
The shape of data
The last digit of each number in the phone
book
The salaries of the employees of a
corporation
The age of retirement for all people in the
US
The heights of all adult women in the US
Stem Plots
Used to display data
Make a stem and leaf plot
32, 67, 89, 54, 98, 28, 59, 68, 75, 94, 49,
58, 100, 97, 76, 84, 82, 86, 94, 57, 67, 78
Histograms
 A bar graph with no
gaps in between.
 The frequencies are
the heights of the
bars.
 The x-axis is divided
into “classes” or
intervals.
Make a histogram…
 75, 65, 121, 100, 101,
89, 114, 63, 123, 127,
100, 96, 116, 109, 92,
131, 134, 105, 108,
117, 90, 89, 101, 101,
89, 98, 104, 130, 128,
97, 113, 129, 106, 87,
107, 68
Class
Freq
6069
7079
8089
9099
100- 110109 119
120- 130129 139
Homework
Exercises 13.1 Worksheet