X-Y Scatter Plot Guidelines

Use an X-Y when you want to show relationships between two measures.  Examples of relationships to graph with an X-Y include:

Yearly Average Global Temperature and Number of Hurricanes

Shoe size and height

Country latitude and frequency of skin cancer

Average hours of sleep per night and GPA

Average calories consumed per day and weight

Average country rainfall and number of species of frogs

Hours practicing a musical instrument and SAT Math scores

Do NOT use an X-Y scatter plot to show change over time.  Time series data should be graphed with a line graph, or bar, or column graph.

X-Y scatter plots are especially useful to show relationships between pairs of measurements that have very different scales.  For example, if you were interested in seeing if there was any relationship between average literacy rate of women and what year women received the right to vote in all the countries of the world.  Literacy rate is a percentage (0-100), and year received vote varies between 1838 (Pitcairn Island)  - 2004.  The scale on one axis varies between 0-100, where the scale on the other axis varies between 1838-2004.  If these were plotted together as a bar graph with a single scale 0-2004, the bars for the literacy rate would be so tiny they could not be seen.

This example above almost seems like a time-series, but the question focuses on "is there a relationship between year suffrage and literacy rate" that might suggest cause and effect.  The implication is that countries who early on decided that women could vote, may be a factor affecting the literacy rate of women today.