Presenting Data – Graphs and Tables
Types of Data
There are different types of data that can be collected in an experiment. Typically, we try to design experiments that collect objective, quantitative data.
Objective data is fact-based, measurable, and observable. This means that if two people made the same measurement with the same tool, they would get the same answer. The measurement is determined by the object that is being measured. The length of a worm measured with a ruler is an objective measurement. The observation that a chemical reaction in a test tube changed color is an objective measurement. Both of these are observable facts.
Subjective data is based on opinions, points of view, or emotional judgment. Subjective data might give two different answers when collected by two different people. The measurement is determined by the subject who is doing the measuring. Surveying people about which of two chemicals smells worse is a subjective measurement. Grading the quality of a presentation is a subjective measurement. Rating your relative happiness on a scale of 1-5 is a subjective measurement. All of these depend on the person who is making the observation – someone else might make these measurements differently.
Quantitative measurements gather numerical data. For example, measuring a worm as being 5cm in length is a quantitative measurement.
Qualitative measurements describe a quality, rather than a numerical value. Saying that one worm is longer than another worm is a qualitative measurement.
| Quantitative | Qualitative | |
| Objective | The chemical reaction has produced 5cm of bubbles. | The chemical reaction has produced a lot of bubbles. |
| Subjective | I give the amount of bubbles a score of 7 on a scale of 1-10. | I think the bubbles are pretty. |
After you have collected data in an experiment, you need to figure out the best way to present that data in a meaningful way. Depending on the type of data, and the story that you are trying to tell using that data, you may present your data in different ways.
Data Tables
The easiest way to organize data is by putting it into a data table. In most data tables, the independent variable (the variable that you are testing or changing on purpose) will be in the column to the left and the dependent variable(s) will be across the top of the table.
Be sure to:
- Label each row and column so that the table can be interpreted
- Include the units that are being used
- Add a descriptive caption for the table
Example
You are evaluating the effect of different types of fertilizers on plant growth. You plant 12 tomato plants and divide them into three groups, where each group contains four plants. To the first group, you do not add fertilizer and the plants are watered with plain water. The second and third groups are watered with two different brands of fertilizer. After three weeks, you measure the growth of each plant in centimeters and calculate the average growth for each type of fertilizer.