1. Relative Frequency Graphs
When the proportion or percent
matters more than the raw counts
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2. What’s old and what’s new?
Frequency
Relative Frequency
The horizontal axis has the classes
The vertical axis has the frequencies, the counts
The horizontal axis has the classes
The vertical axis has the relative frequencies
How many in this class
Divided by How many total
Values from 0.00 to 1.00
Or 0% to 100% of the total
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3. Compute the Frequencies
Remember, these graphs and charts all start with a table of data, a Frequency Distribution
The Frequency Column alone isn’t enough.
You need a Relative Frequency column
How many items in each class
Divided by How many total items
Equals a number from 0.00 to 1.00
Equals a percent from 0% to 100%
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4. Bluman’s High Temps Example © McGraw Hill
Original data table (yellow) with relative frequency added (purple)
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5. Old: Histogram, frequency
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6. New: Histogram, relative frequency
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7. Histogram, with Percents
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8. What changed? New – Relative Frequency
Old – Frequency on vertical axis
New – Relative Frequency
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9. What changed? New – Percent of total Old – Frequency on vertical axis
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10. Relative Frequency Polygon
Remember that we plot class midpoints.
Still need Relative Frequency data.
And dummy classes to anchor the polygon at either end.
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11. Relative Frequency Polygon data
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12. Original Frequency Polygon Vertical axis has the actual counts
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13. Relative Frequency Polygon Vertical axis has decimal proportion
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14. Relative Frequency Polygon Vertical axis has percent
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15. Relative Frequency Ogive
Remember that the Ogive is cumulative.
We plot the total number in this class and all the lower classes preceding it.
It grows higher and higher from left to right.
Remember that we plot class high boundaries on the horizontal axis. All data ≤ boundary.
We need cumulative Relative Frequency data.
And a dummy class to anchor the ogive at its left end.
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16. Relative Frequency Ogive Data
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17. Original Ogive – Cumulative Counts
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18. Relative Frequency Ogive Vertical axis has the proportion
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19. Relative Frequency Ogive Vertical axis has the percent
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