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Chapter 5
Describing Distributions Numerically
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View Full Document Center
•
When we think of a typical value, we usually look
for the center of the distribution.
•
Where do you think the center of a distribution is?
•
For a unimodal, symmetric distribution, it’s easy.
Median
•
The middle value that divides the histogram
into two equal areas is called the median.
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View Full Document How to find the Median
•
First, the values have to be in numerical
order.
•
If n (the number of values) is odd, the
median is the middle value. Counting in
from the ends, we find this value in the
position.
2
1
+
n
(cont.)
•
If n is even, there are two middle values. In
this case, the median is the average of the
two values in positions
.
1
2
and
2
+
n
n
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View Full Document Example
•
Here are costs of 10 electric smoothtop
ranges rated very good or excellent by
Consumer Reports in August 2002.
$850
900
1400
1200
1050
1000
750
1250
1050
565
Finding the Median of the
Example
•
First, the numbers have to be in numerical order:
565
750
850
900
1000
1050
1050
1200
1250
1400
•
Since n is even (10 values), the 2 middle values
is found in the 5
th
and 6
th
positions from either
end (1000 and 1050). The average of those 2
values gives us the median of 1025.
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View Full Document Take away 1400
565
750
850
900
1000
1050
1050
1200
1250
•
Now that n is odd, the median is found in
the 5
th
position which is 1000.
•
The range of the data is defined as the
difference between the max and min values.
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This note was uploaded on 04/07/2008 for the course MAT 108 taught by Professor Lamatina during the Spring '08 term at SUNY Albany.
 Spring '08
 lamatina
 Statistics

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