Organizing Data
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Displaying data in a chart is a good way of
organizing your data, however GRAPHS
are invaluable when it comes to organizing
your data
WHY?????
With graphs you can determine any trend
in the data.
However it is very Important to use the
proper type of graph
Bar Graph
Represents discrete data (counted or categorical). The vertical
bars are equally set apart and are used to display quantities.
A double bar graph can be used to compare two sets.
Data categories are Nominal typically
Distance Travelled on Our Vacation
When Do I use it?
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Sunday
250
200
Distance 150
100
(km)
50
0
Day of the Week
• comparing data sets
easily
•Only with discrete
data
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Broken-Line Graph
Involves time-dependent numerical
data. Examples of some broken-line
graphs are temperature vs day or
distance vs time (speed). These plots
are useful for indicating trends.
Patient's Mass
77
When Do I Use It?
76.5
•To show values between known
data. Simple and easy to
visualize
75.5
75
•Makes many assumptions
74.5
74
June
26th
June
19th
June
12th
73.5
June
6th
Mass (kg)
76
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Circle Graph
or Pie Chart
Countries Visited
England
25%
France
40%
Displays data as a
percentage. Each
pie section should
have a label and
percentage. A total
data number should
be included.
Belgium
5%
Spain
20%
Portugal
10%
When Do I Use It?
•Harder to compare between sets but good to demonstrate data
compared to overall.
•No exact numerical data is given
•Best with 3-7 categories
•Used only with discrete data
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Pictograph
Uses an icon to represent a quantity of
data values in order to decrease the size
of the graph.
A key or legend must be used to
describe the icon
When Do I Use It?
•Visually Appealing
•Handles large data sets easily
•Hard to quantify partial icons
•Best for small amount of categories
•Very simplistic
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Histogram or Frequency
Diagram
Histograms displays continuous data in ordered
columns. It is a bar graph where bars based on
the frequency of the data being measured.
Unlike the bar graph there is no separation
between the bars and the criteria is now in
equal intervals of measurement
When Do I use it?
•Used to make comparisons, particularly against the “bell” curve
•Only use with Continuous data
•Limited to one data set
•Visually Appealing
A Histogram
FREQUENCY
The bars show how many
times numbers in that
interval are found.
There are 4 pieces of data
in the interval [40, 50)
8
6
4
2
0
40
50
60
70
80
90
100
INTERVALS
What Graph to Use?
Situation
We want to compare total revenues
of five different companies.
Bar Graph or Histogram?
BAR
We have measured revenues of
several companies. We want to
compare numbers of companies
that make from $0 to $10,000;
from $10,000 to $20,000; from
$20,000 to $30,000 and so on.
HISTOGRAM
We want to compare heights of ten
oak trees in a city park.
BAR
We have measured several trees in a
city park. We want to compare
numbers of trees that are from 0
to 5 meters high; from 5 to 10;
from 10 to 15 and so on.
HISTOGRAM
Making a Histogram
HISTOGRAMS
Step 1
Create a Frequency Table
Interval
[ , )
[ , )
Tally
||||
The Intervals are all equal in length
Frequency
4
Histograms
FREQUENCY
The bars show how many
times numbers in that
interval are found.
There are 4 pieces of data
in the interval [40, 50)
8
6
4
2
0
40
50
60
70
80
90
100
INTERVALS
Step 2
Create Histogram
Example
Students planning on going to a
particular College have submitted
their marks
75,78,69,88,89,91,79,74,66,58,82,
70,74,75,70,58,72,82,86,70,76,88,
60,78,77,86,65,74,85,70,76,88,70,
78,76,80,76
Create a Histogram by Hand and
summarize the results
Relative Frequency
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You can add another column to your
frequency table which shows the
frequency of data group as a fraction
or percent of the whole data set
If there is a frequency of 1 out of 30
pieces of data then your relative
frequency is 0.033

You can graph this on your
histogram as a broken line graph
Excel

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Enter Data into your first column
Range is 15 degrees so 2 degree
Decide on interval intervals would work. Start at 17.5
and end at 33.5
Enter Midpoints into second column
Use Data Analysis Option in the Tools
Menu
Follow instructions to create
Histogram
Fathom *Recommended*
on L: drive under Math Department
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Drop Chart into main page
Enter in data
Drag chart option onto main page
Drag data into chart
Choose Histogram style
Alter intervals if needed
Homework
Pg 101 #1, 2, 5, 8 use fathom to
create a histogram, 15