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Graphs, Charts, and Graphs, Charts, and Tables - Describing Tables - Describing
Your DataYour Data
©
Frequency DistributionsFrequency Distributions
A frequency distributionfrequency distribution is the sum of a set of data that displays the number of observations in each of the distributions distinct categories or classes.
Frequency Distribution of Years in Frequency Distribution of Years in CollegeCollege(Figure 2-1)(Figure 2-1)
City #1Years of College Frequency
0 351 212 243 224 315 136 67 58 3
Total 160
Relative FrequencyRelative Frequency
The relative frequencyrelative frequency is the proportion of total observations contained in a given category.
n
fRF i
Relative Frequency Distribution of Relative Frequency Distribution of Years in CollegeYears in College
(Figure 2-3)(Figure 2-3)
City #1Years of College
RelativeFrequency
0 35/160=0.2191 21/160=0.1312 24/160=0.1503 22/160=0.1384 31/160=0.1945 13/160=0.0816 6/160=0.0387 5/160=0.0318 3/160=0.019
Total 1.000
Grouping Data Into Grouping Data Into ClassesClasses
Continuous data: Data whose possible values are uncountable and which may assume any value in an interval.
Data array: Data that have been sorted in ascending or descending order.
Mutually exclusive classes: Classes that do not overlap.
All inclusive classes: A set of classes that contains all the possible values.
Equal width classes: Distance between lowest possible value and highest possible value in each class is the same.
Steps for Grouping Data Steps for Grouping Data Into ClassesInto Classes
Step 1: Determine the number of groups or classes to use.
Step 2: Establish the class width.
Class WidthClass Width
Classes ofNumber ValueSmallest - ValueLargest
W
Steps for Grouping Data Steps for Grouping Data Into ClassesInto Classes
Step 1: Determine the number of groups or classes to use.
Step 2: Establish the class width.
Step 3: Determine the class boundaries for each class.
Steps for Grouping Data Steps for Grouping Data Into ClassesInto Classes
Step 1: Determine the number of groups or classes to use.
Step 2: Establish the class width. Step 3: Determine the class
boundaries for each class. Step 4: Count the number of
values in each class.
Frequency HistogramsFrequency Histograms(Figure 1-2)(Figure 1-2)
BAKER CITY HOSPITAL - LENGTH OF STAY DISTRIBUTION
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0<2 2<4 4<6 6<8 8<10 10<12 12<14 14<16 16<18
Frequency HistogramsFrequency Histograms
A histogram shows three general types of information:
It provides visual indication of where the approximate center if the data is.
We can gain an understanding of the degree of spread, or variation, in the data.
We can observe the shape of the distribution.
Histograms Showing Histograms Showing Different CentersDifferent Centers
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0<2 2<4 4<6 6<8 8<10 10<12 12<14 14<16 16<18
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0<2 2<4 4<6 6<8 8<10 10<12 12<14 14<16 16<18
Histograms - Same Center, Histograms - Same Center, Different SpreadDifferent Spread
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