Rules for Making Perfect Graphs (and improving your Biology Grades!)

There are 6 Important parts to most scientific graphs: 1. Title 2 There are 6 Important parts to most scientific graphs: 1. Title 2. Intervals 3. Labels 4. Data 5. Legends or Keys 6. Neat & easy to read

1. Title: The title on a graph first is the first clue to the reader as to what the data collected for the graph is about. The title must have both the dependent (measured or responding) & independent (changed or manipulated) variables in it. It tells the relationship between the variables shown in the graph. Examples of graph titles: Bad: Plant Growth Good: The Effect of Carbon Dioxide on Plant Growth Bad: Speed Graph Good: How Leg Length is Related to a Person’s Speed The bad titles don’t give the reader any idea of what the experiment is really about. They are generally not specific enough about what was tested and how it was done. Always mention the names of what you are changing (manipulated/independent variable) and what you are measuring (responding /dependent variable) in the title. The independent/manipulated variables above are amount of carbon dioxide and leg length, what was measured (dependent/responding variables) is plant growth and a person’s speed.

2. Intervals Intervals on both the x and y-axes must fit the size of the graph. The numbers should be equal, evenly spaced units. The values may increase or decrease, depending on the graph, but spacing should be equal. -One of the most common errors made when creating a graph is to begin numbering the graph paper before a check is made to see if the data will fit on it. This leads to extra and/or messy work. -a second common error is to label the graph grids with different spacing values so that the intervals are not equal. For example, labeling consecutive grids with as 1, 3, 12, 19, & 23 will make your graphed data less accurate and confusing.

3. Labels Both axes must be labeled with the Variables name and the Units that were used. Manipulated/Independent variables are always placed on the X-axis and the Responding/ Dependent variables, which scientists measure or count, are graphed on the Y-axis. Graphs without units are confusing since they don’t have all the information on them. Units are very important since they tell the reader a lot of information about the scale of the measurement and how an experiment was done. An experiment that measures plant growth in inches per day is very different than one that measures plant growth in pounds gained per month. No units = lose points.

4. Data Data must be correctly graphed. Be careful to make the correct points on the graph and then to draw a “line of best fit” curve. There may be some points that don’t exactly fit on the curve, but draw a curve that goes between two close points (showing what the average for those two might be) or that has the most number of points on the curve. Remember a “curve” in terms of graphing can be a straight line.

5. Legends or keys LEGENDS or Keys- must be used when there is more than one line, bar or piece of pie on the graph. This allows the reader to “easily” read and figure out the differences in different data curves. You can use different colors, line types or shapes (triangles, diamonds, circles, boxes, etc.) to represent different parts of the graph.

6. Neat All graphs must be neat and easy to read. Always use graph paper, a pencil to initially draw the graph and add data and a ruler to make straight lines (if needed).

Types of Graphs & how they can be used: Line Graphs: Most often used in science, shows continuous quantitative (numbers) data (e.g. time, height, etc.) They show how the responding variable changes because of the manipulated variable Circle (Pie) Graphs: Show parts of a whole Bar Graphs: Show comparisons of data with specific, discreet categories (e.g. types of pets)