How to Interpret Tables, Graphs & Charts of Scientific Data: Practice Problems

Instructor: Laura Foist

Laura has a Masters of Science in Food Science and Human Nutrition and has taught college Science.

In this lesson, we will look at some practice problems involving tables, graph, and charts. We will specifically look at x- and y-axis graphs, pie charts, and bar graphs.

General Information

A graph can seem very confusing when you first look at it. All of those lines and points just don't seem to make any sense. But a graph can be a very easy way to quickly see the data. We simply need to understand how to read graphs, tables, and charts.

For any graph, chart, or table, one of the first things you want to look at are the headings and units used. This will tell you a lot about what is being represented in the data. If a line on a graph says 'years' then you already know that this is some sort of timeline. If a heading says 'percentage who did homework' then you know that in this table column there will be a list of percentages and these are those who did their homework.

The x- & y-axis Graphs

The most common type of graph used in science is the x- and y-axis graphs. The x- and y-axis graphs are graphs that show numbers vertically and horizontally to see how they compare and affect each other.

Here is what the graph looks like:

axis graph explained

The vertical line is the y-axis, and the horizontal line is the x-axis. Typically the origin (where the two lines meet) denotes (0, 0). In other words, this is 0 for both the x-axis and for the y-axis. As you move up the y-axis or to the right along the x-axis, you get increasingly higher positive numbers. As you move down the y-axis or to the left along the x-axis, you get decreasingly lower negative numbers.

Most of the time, the negative portion of the graph isn't shown and only this section is shown:


Which ends up looking like this:


Interpreting x- & y-axis Graphs

We often use x- and y-axis graphs for showing the activity of enzymes, reaction rates, and activation energy.

For most enzymes there is an ideal temperature, pH, or concentration. So, anything building up to that ideal will increase the enzyme activity. Yet, anything above that ideal will either have no effect on the enzyme activity or cause the activity to decrease. This can typically be shown using graphs. Let's look at a few examples of enzyme activity and see if we can understand what is happening. Let's look at the graph:

Enzyme Activity and Temperature

First, we need to note what each axis represents. The x-axis represents temperature in degrees Celsius. And we see that this graph shows a range from about 0-35 degrees Celsius. The y-axis represents enzyme activity as a percentage.

As we go along the x-axis, we first see that the line is going higher. So as we increase the temperature, the enzyme activity increases. This continues until we get to about 28 degrees Celsius. Then it starts to decrease again. So, we know that about 28 degrees Celsius is the optimum temperature for this reaction to occur.

Now let's determine the optimum pH:

Enzyme Activity and pH

What do you first see? What does the x-axis represent? How about the y-axis? The x-axis represents pH on a range from 0-14. The y-axis again represents enzyme activity as a percentage.

This reaction does not increase in activity very rapidly at a lower pH. It isn't until about a pH of 3 that we really start to see an increase in activity. Then it rapidly increases in activity until about a pH of 7 at which point it slowly starts to decrease in activity. So, the optimum activity is at a pH of 7.

The third example is of Enzyme activity and substrate concentration:

Enzyme Activity and Substrate Concentration

Let's start with the basics. What is the x-axis? What is the y-axis? So the x-axis represents the substrate concentration, and the y-axis, again, represents the enzyme activity. At what substrate concentration does the enzyme activity plateau (stop increasing)? We can look at the graph and see that it is at about 30%. At this point, the enzyme activity neither increases nor decreases any further.

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