Graph Types

Graphing 

Graphs and charts communicate information visually. 

They can show patterns, help scientists identify correlations, and get the point of the experiment across quickly. 

The independent variable is plotted on the x-axis 

The dependent variable is plotted on the y-axis. 

The mnemonic DRY MIX, for “dependent, responding, y-axis” and “manipulated, independent, x-axis,” can help you remember this pattern. 

Label both axes (independent variable on the X-axis and dependent variable on the Y-axis) Include units on both axes. Enclose the unit in parentheses. 

Provide a descriptive title. Use the pattern, “The Effect of the independent variable on the dependent variable”. For example ,if you were graphing the miracle-gro concentration against plant height. The title of the graph might be “The Effect of Miracle-Gro Concentration on Plant Height”. If the instruction is to plot rather than graph the data points, no line needs to be drawn.

Which Graph Type To Use?

 A) Line Graphs: are used for looking at the relationship between two continuous types of data. Typically, both the independent and dependent variables are numerical. 

B) Bar Graphs: are used for making comparisons between discrete cases or to look for trends, such as over space or time. The independent variable is usually a category and the dependent variable is usually an average, percentage, or frequency. 

C) Scatter Plot: Scatter plots are used for examining relationships between two types of data. These are very similar to line graphs, just without the line. 

Line graphs provide an excellent way to map independent and dependent variables that are both quantitative. When both variables are quantitative, the line segment that connects two points on the graph expresses a slope, which can be interpreted visually relative to the slope of other lines or expressed as a precise mathematical formula. Scatter plots are similar to line graphs in that they start with mapping quantitative data points. The difference is that with a scatter plot, the decision is made that the individual points should not be connected directly together with a line but, instead express a trend. This trend can be seen directly through the distribution of points or with the addition of a regression line or line of best fit. 

D) Box-and-whisker plots allow graphical comparison of two samples of nonparametric data (data that do not fit a normal distribution).

E)  Histograms, or frequency diagrams, are used to display the distribution of data, providing a representation of the central tendencies and the spread of the data

Generally you will not see pie charts on AP Bio.

Box and Whisker

Khan Academy: Box and Whisker

Review Video: