1. Types of Graph
And when to use them!

2. Line Graph

3. Line Graph Used to show trends
Variable plotted on X (bottom) musts be continuous
Common type is “time series” where X = time
CANNOT be used to graph data where X is discrete

4. Scatterplot

5. Scatterplot Used to show relationships between variables
X variable must be continuous
If one variable is believed to cause or explain changes in the other, that variable is plotted on the X

6. Bar Graph

7. Bar Graph
Used to compare amounts or frequencies in data that represents different categories (discrete data sets)
Categorical data set is plotted on X, quantitative (continuous) on the Y
Often used incorrectly to graph data with continuous X variables

8. Histogram

9. Histogram Used when discrete X is converted to categories (“bins”)
Y represents frequency of data within each “bin”

10. Pie Chart

11. Pie Chart Used for same kind of data as bar chart
Each slice = data category
Slice size shows relative proportion of observations within each category

12. Summary: Types of Graph
Graph type
Use
Line graph
Connects dots with lines
Used for continuous X data
Show patterns or trends
If time = X, time-series graph
Scatterplot
Display/assess relationship between variables
Bar graph
Used to show patterns
Should only be used when X data are categorical

13. Graph type
Description
Histogram
Similar to bar graph, but used when continuous X data are converted to categories
Pie chart
Compares small number of categories.
Works best if values are very different.
If similar, should label pie segments with actual values