Understanding Data Presented in Tables & Graphs

Instructor: Betsy Chesnutt

Betsy teaches college physics, biology, and engineering and has a Ph.D. in Biomedical Engineering

Data is often presented in tables and graphs to make it easier to understand and interpret. In this lesson, you will learn about several types of tables and graphs, and develop the skills needed to understand them.

Visual Representations of Data

Fields as diverse as finance, science, and politics all rely heavily on interpreting large amounts of numerical data. This can be challenging for many people, and so tables and graphs are used to present the data in a way that is easy to understand.

Although there are many different types of tables and graphs, you can interpret them all if you remember some basic guidelines.

  1. First, look at the title and any other labels. Some graphs may have a legend that will give you important information. The axis labels can also tell you a lot about the information presented in the graph.
  2. Next, look carefully at the graph to identify the important information that you need to know and then use that information to answer the question.

Let's look at a few different types of tables and graphs and see how to understand the information presented in each.

Tables

Tables are the simplest way to represent data. A table compiles all the data into a columns and rows so that it can be easily interpreted. The table below shows the average number of visitors per day at two different lakes over an eight year period. By looking at the row and column titles, you can see that each row corresponds to a different year, and each column to a different lake.


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You could use a table like this to answer a lot of different questions. For example, which lake had more visitors in Year 5?

The table shows that in Year 5, Lake Itawamba had an average of 74 visitors per day and Lake Tishomingo had an average of 85 visitors per day, so Lake Tishomingo had more visitors in Year 5.

Pictographs

A pictograph uses images to to represent a certain number of items. For example, suppose you had a lemonade stand and wanted to record how much lemonade you sold each day. Using the following pictograph, determine how many glasses of lemonade you sold on Thursday:


In this pictograph, one lemon represents 10 glasses of lemonade sold
pictograph of lemonade sales


Did you get 40 glasses of lemonade? Great!

Looking at the pictograph, you can see that there are four lemons on the line that says Thursday, and you also know that each lemon represents 10 glasses of lemonade. This means that you sold 40 glasses of lemonade on Thursday.

Line Graphs

A line graph plots individual data points as dots and connects them with lines. These are great if you want to see how a quantity is changing over time. The line graph below represents the distance an object travels over time. Even though there is no title, you can look at the axis labels and see that the x axis measures time and the y axis measures distance.


distance time graph


Using this graph, you could find the position of the object at any time. You could also use this graph to determine that the object was speeding up, because the difference in distance between any two consecutive seconds is increasing.

Bar Graphs

Bar graphs use bars of different heights to represent data. As with the other types of graphs, you first want to read the title and the axis labels to make sure you understand what data is being presented. In the bar graph shown below, you can see that the x axis has months and the y axis says Temperature. Therefore, this graph is showing you the average temperature during each month of the year at a certain location.


bar graph of average daily temperature


Now you are ready to analyze and use the data presented in the graph. Can you use the graph to calculate the temperature difference between the warmest and the coldest month of the year?

First, you need to determine which month is the warmest and which is the coldest. Looking at the graph, we can see that January is the coldest and July is the warmest. Next, note the average temperatures in both January and July. In this graph, the average temperature in January is about 30 degrees and the average temperature in July is about 75 degrees. Finally, subtract the two temperatures to find the temperature difference:

75 degrees - 30 degrees = 45 degrees

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