Relative Frequency Graphs When the proportion or percent matters more than the raw counts 1/17/2019
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 1/17/2019
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% 1/17/2019
Bluman’s High Temps Example © McGraw Hill Original data table (yellow) with relative frequency added (purple) 1/17/2019
Old: Histogram, frequency 1/17/2019
New: Histogram, relative frequency 1/17/2019
Histogram, with Percents 1/17/2019
What changed? New – Relative Frequency Old – Frequency on vertical axis New – Relative Frequency 1/17/2019
What changed? New – Percent of total Old – Frequency on vertical axis 1/17/2019
Relative Frequency Polygon Remember that we plot class midpoints. Still need Relative Frequency data. And dummy classes to anchor the polygon at either end. 1/17/2019
Relative Frequency Polygon data 1/17/2019
Original Frequency Polygon Vertical axis has the actual counts 1/17/2019
Relative Frequency Polygon Vertical axis has decimal proportion 1/17/2019
Relative Frequency Polygon Vertical axis has percent 1/17/2019
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. 1/17/2019
Relative Frequency Ogive Data 1/17/2019
Original Ogive – Cumulative Counts 1/17/2019
Relative Frequency Ogive Vertical axis has the proportion 1/17/2019
Relative Frequency Ogive Vertical axis has the percent 1/17/2019