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Lecture 4

STAB22 Lecture 4: Statistics I: Lecture 4.docx


Department
Statistics
Course Code
STAB22H3
Professor
Shrista
Lecture
4

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Statistics I
Lecture 4: Quantitative Data: How to display and summarize
Review
Why need to display data?
Different ways of displaying Categorical Data? - Bar Chart, Pie Chart,
Contingency Table
Contingency Table review
Recall
Quantitative data - It can be measured (with units), i.e., it takes numerical values.
Since, we don’t have any categories in quantitative data, the method of displaying its
distribution differs from that of categorical data.
Displaying Quantitative
There are different ways to display the distribution of quantitative data:
1. Histogram
2. Stem - and - Leaf Plot / Display
3. Dotplots
Histogram
Since, we don’t have categories in quantitative data, we divide the values into
equal - sized bins or classes
Just like a bar chart, we have the vertical (y - axis) to be the frequency for the
data, i.e., the count / percent observations in classes
What is the difference between a histogram and a bar chart?
Example
Page 79, Data from Q. 14.
Annual numbers of deaths from tornadoes in the United States from 1990 through 2000.
53 39 39 33 69 30 25 67 130 94 40
Let’s create a histogram!
Stem - and - leaf plot / display
It is like a histogram, except, it shows the individual values in addition to the
shape of the data.
How can we get this plot with the data given?
Example revisited
53 39 39 33 69 30 25 67 130 94 40
Again, first step - Sort the data to write them in ascending order.
25 30 33 39 39 40 53 67 69 94 130
Second step - Establish the leaf unit. In this case, leaf unit=1
Third step - Display data.
Example revisited
Stem - and - leaf plot
Leaf unit = 1 2 I 5
3 I 0 3 9 9
4 I 0
5 I 3
6 I 7 9
7 I
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