How to Graph
- Click to review the different types of graph
- Click to view a checklist for completing graphs.
- Click to learn how to graph in Excel.
- Click to learn how to graph in Sheets.
- Click to learn about interpreting error bars on graphs.
- Click to read a short article about the effective use of graphs.
Properly constructed graphs communicate findings clearly and support scientific arguments. Every graph should include several critical components to meet both IB and general scientific expectations.
1. Title
The graph must have a title which should describes what the graph shows, mentioning both variables. If there is more than one graph, a reference number or letter is required. For example: “Fig 2: A graph showing the change in testis weight throughout the year in the brown rat (Rattus rattus)” IS BETTER THAN... “A graph of testis weight against time” which is insufficient. Underline or use bold type for your title it makes it stand out and is easier to find on the page.
The graph must have a title which should describes what the graph shows, mentioning both variables. If there is more than one graph, a reference number or letter is required. For example: “Fig 2: A graph showing the change in testis weight throughout the year in the brown rat (Rattus rattus)” IS BETTER THAN... “A graph of testis weight against time” which is insufficient. Underline or use bold type for your title it makes it stand out and is easier to find on the page.
2. Axes Labels and Units
Manipulated (independent) variables and always go on the horizontal axis (x—axis). The responding (independent) variable is always plotted on the vertical axis (y—axis or ordinate). Each axis must be labeled with the variable it represents and its unit in parentheses. For example, the x-axis might read "Temperature (°C)" and the y-axis "Rate of Reaction (mol/min)".
Manipulated (independent) variables and always go on the horizontal axis (x—axis). The responding (independent) variable is always plotted on the vertical axis (y—axis or ordinate). Each axis must be labeled with the variable it represents and its unit in parentheses. For example, the x-axis might read "Temperature (°C)" and the y-axis "Rate of Reaction (mol/min)".
3. Appropriate Scale
Choose a scale that uses most of the graph area and makes differences in data easy to see. The area enclosed by the axes should be roughly square and not disproportionately exaggerated. Scales should increase in equal increments. Axis intervals do not have to be the same on the x and y axis and they do not have to always start at the origin with a value of 0.
Choose a scale that uses most of the graph area and makes differences in data easy to see. The area enclosed by the axes should be roughly square and not disproportionately exaggerated. Scales should increase in equal increments. Axis intervals do not have to be the same on the x and y axis and they do not have to always start at the origin with a value of 0.
4. Plotting Data Points
Plot points accurately using small, neat dots. If plotting multiple data sets, use different symbols or colors and include a key/legend.
Plot points accurately using small, neat dots. If plotting multiple data sets, use different symbols or colors and include a key/legend.
5. Line or Curve of Best Fit
For continuous data (e.g., time, temperature), draw a smooth line or curve of best fit—not simply connecting the dots. Look at the points on the graph and make an estimation of which, if any, shape of trendline best fits your data.
For continuous data (e.g., time, temperature), draw a smooth line or curve of best fit—not simply connecting the dots. Look at the points on the graph and make an estimation of which, if any, shape of trendline best fits your data.
6. Error Bars
If the data includes variability such as (standard deviation or standard error), add error bars.
If the data includes variability such as (standard deviation or standard error), add error bars.
7. Legend/Key
If more than one data set is shown, provide a legend identifying each set.
If more than one data set is shown, provide a legend identifying each set.
8. Neatness and Clarity
Graphs should be drawn with a ruler (for axes and lines), be free of extraneous marks, and have readable text. Digital graphs should be checked for clarity and formatting.
Graphs should be drawn with a ruler (for axes and lines), be free of extraneous marks, and have readable text. Digital graphs should be checked for clarity and formatting.
