Histogram
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Definition
Histogram

Tip: When creating a histogram...
 Leave no space between bars when the class intervals represent continuous data; bar graphs, drawn with a gap between bars, are used to represent discrete data (i.e., different categories).
 Graph the observed frequency in each class interval (also called the class frequency) for datasets with a small to medium number of observations; label the yaxis "Frequency." Graph the relative frequency in each class interval for datasets with a large number of observations; label the yaxis "Proportion" or "Relative Frequency."
Contents
Examples
A typical histogram
Pulse rates, in beats per minute, were calculated for 192 students enrolled in a statistics course at the University of Adelaide.^{[1]} The first step in creating a histogram is to create a frequency table.
Pulse Rate  Count 

(3441]  2 
(4148]  2 
(4855]  4 
(5562]  19 
(6269]  40 
(6976]  53 
(7683]  30 
(8390]  27 
(9097]  10 
(97104]  5 
Total  192 
Using the class frequencies (the number of observations in each class interval) shown in the frequency table, the following histogram was created.^{[2]}
Exploring the effect of class interval size
See West's histogram applet for an opportunity to experiment with different class interval sizes.
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