Often in science we will collect data in order to answer a question. We will normally present this data in a table so it is easy to see and so they are organized in a clear and meaningful way. Tables are great for seeing all the data and they make data collection very easy. However, they are not the best way to see trends or relationships between the data sets.
All graphs show a relationship between two or more variables. The variables that are graphed are called dependent and independent variables. The independent variable is the condition that you change. For example, if you are testing which brand of phone is the most popular your independent variable would be the different types of phones.
The other variable is the dependent variable. You might have heard this variable called the responding variable. The dependent variable is the variable that you measure. In the phone example above the dependent variable would be the number of each type of phone students at St. Francis own.
When graphing data the independent variable is always on the x-axis and the dependent variable is always on the y-axis.
Scientists use graphs to clearly illustrate whether or not there is a relationship between variables. There are four main types of graphs; a scatterplot, a bar chart, a line graph, and a pie chart. Each of these graphs is used for a showing a different type of data.
All graphs show a relationship between two or more variables. The variables that are graphed are called dependent and independent variables. The independent variable is the condition that you change. For example, if you are testing which brand of phone is the most popular your independent variable would be the different types of phones.
The other variable is the dependent variable. You might have heard this variable called the responding variable. The dependent variable is the variable that you measure. In the phone example above the dependent variable would be the number of each type of phone students at St. Francis own.
When graphing data the independent variable is always on the x-axis and the dependent variable is always on the y-axis.
Scientists use graphs to clearly illustrate whether or not there is a relationship between variables. There are four main types of graphs; a scatterplot, a bar chart, a line graph, and a pie chart. Each of these graphs is used for a showing a different type of data.
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Scatterplots are used when the independent variable is continuous. Continuous data is when there is an infinite range in data points that are possible. For example, it is possible to have a temperature of 30 degrees or a temperature of 31 degrees. It is also possible to have a temperature of 30.6 degrees. In continuous data there are no distinct categories. Age is an example of continuous data. If you could measure your data in more precise detail then your data is probably continuous.
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On the other hand, bar graphs are normally used when you have discontinuous data. Discontinuous data has distinct values/categories and there are no in-between values. Discontinuous data tends to be qualitative, or not having a number. For example, fruit types are discontinuous; the fruit is either an apple, an orange, or a pear. If you were graphing how many of each type of fruit were sold at lunch then you would use a bar graph.
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Line graphs are used when you want to track what happens over time. Line graphs are great for displaying how temperature changes as you heat a container of water or the amount of CO2 in the atmosphere from one decade to the next.
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Last but not least, pie charts are most often used to show percentages. Pie charts make it easy to see a part of the whole in the same way that a percent tells you the part of a whole.
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