X-Axis

• The x-axis of a graph is the horizontal line running side to side. Where this line intersects the y-axis, the x coordinate is zero. When using a graph to represent data, determining which variable to put on the x-axis is important because it should be the independent variable. The independent variable is the one that affects the other. For example, if you were plotting time worked against dollars made, time would be the independent variable because time would pass regardless of income. You must also chose a proper scale for the graph and label it with the proper units. For example, if you did an experiment with different amounts of fertilizer to see its effect on plant growth, the scale should go from zero to the maximum amount of fertilizer you used. Let's say you used 1 cup for 5g fertilizer for one group, 10g for another group and 15g for a third group. Your scale could be marked off every 5g, and the title below the x-axis would be "Fertilizer (grams)." If you didn't include the unit of measure, people reading the graph wouldn't know if you gave each plant 5g, cups or lbs. of fertilizer.
  
  

Y-Axis

• The y-axis of the graph is the vertical line running top to bottom. Where this line intersects the x-axis, the y coordinate is zero. When using a graph to represent data, determining which variable to put on the y-axis is important because it should be the dependent variable. The dependent variable is the one that is affected by the other. For example, if you were plotting time worked against dollars made, dollars made would be the dependent variable because the amount made depends on how many hours were worked. You must also choose a proper scale for the graph and label it with the proper units. For example, if you did an experiment with different amounts of fertilizer to see its effect on plant growth, the scale should go from zero to the maximum amount a plant grew. Let's say one group averaged 8cm of growth, the second averaged 15cm of growth and the last group averaged 10cm of growth. The scale could go from zero to 15, and the y-axis title would be "Growth (centimeters)." If you didn't add the unit of measure, people wouldn't know if you were talking about growth in millimeters, inches or miles.
  
  

Title

• Place a title on the graph, which is important because it summarizes what the graph is showing. The title is usually placed in the center, either above or below the graph. The title of the graph should be in terms of what the x and y axes represent. The proper form is "y-axis variable vs. x-axis variable." For example, if you were comparing the the amount of fertilizer to how much a plant grew, the amount of fertilizer would be the independent, or x-axis variable and the growth would be the dependent, or y-axis variable. Therefore, your title would be "Amount of Fertilizer vs. Plant Growth."