Recording and Graphing Data

Graphing Rules

1. The independent variable is plotted on the abscissa (also called the x-axis or horizontal axis), while the dependent variable is plotted on the ordinate (also called the y-axis or vertical axis). The dependent variable is the one whose value changes as a result of changes in the independent variable. In our example, study time was the independent variable, grade received was the dependent one. The grade depended on the amount of studying done, not vice versa. Each axis should be clearly labeled with the quantity that is being plotted.

2. The axes' scales should be numbered such that the data fills as much of the graph paper as possible. The scale should also make subdivisions as even as possible. A scale that has subdivisions of one tenth of a unit (0.1) would be good, one with subdivisions of one eighth (0.125) would be bad. This graph has horizontal subdivisions of 1 hr and vertical divisions of 10 points. The scale must also contain units if the quantity being graphed has units. Units are usually placed in parentheses following the axis label. Study time on this graph has units of hours while the grades were based on percent.

3. The data points should be plotted as small x's or a circled dot. Small dots all by themselves are difficult to see and should be avoided.

4. The graph should have a title. The title should describe why the graph was constructed. Try to avoid simply restating the axis labels.

Continue and read about determining a best fit line.