charts present frequency distributions graphically Graphs and charts are commonly used ways of presenting “pictures” of research results Graphs and charts are very useful ways to display the overall shape of a distribution
Sample Pie Chart: Religious Identifications, 2008 Pie charts are useful for discrete variables with only a few categories. The pie is divided into segments which are proportional in size to the percentage of cases in each category.
Sample Bar Chart: Religious Identifications, 2008 Bar charts are useful for discrete variables. The categories are represented by bars. The height of these bars corresponds to the number or percentage of cases in each category.
Sample Bar Chart: Comparing Two Variables
Histograms Most appropriate for continuous interval-ratio level variables, but can be used for discrete interval-ratio level variables Look like bar charts Use real limits instead of stated limits Categories (or scores) of the variable border each other (the sides of the bars touch)
Constructing a Histogram from a Frequency Distribution 1. Array the real limits of the class intervals or scores along the horizontal axis (abscissa) 2. Array frequencies along the vertical axis (ordinate) 3. For each category, construct a bar with height corresponding to number of cases and width corresponding to real limits of class intervals 4. Label each axis of graph 5. Title the graph
Sample Histogram: Age, 2010
Line Charts Sometimes called frequency polygons Constructed similarly to a histogram, except graph a dot at each category’s midpoint and then connect the dots Especially appropriate for continuous interval-ratio level variables , but can be used for discrete interval-ratio level variables
Sample Line Chart: Age, 2010
Line Charts: Marriage And Divorce Rates Over Time How would you describe the patterns?
- Fall '19
- Bar chart, Joseph F. Healey, 46.58%