# How to Construct Graphs from Data

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• 0:01 What Are Graphs & How…
• 2:32 Pie Graphs
• 5:07 Line Graphs
• 9:23 Lesson Review

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Lesson Transcript
Instructor: Paul Brege

Paul has been teaching middle school science for the last 10 years, and has his bachelors degree in Elementary Education.

This video describes how to create a line graph and explains the four main parts that graphs need to contain: 1. previously collected data, 2. picture representations, 3. use of the correct graph type, and 4. labels. This lesson also covers dependent and independent variables.

## What Are Graphs and How do I Make Them?

You can make wallets with it, fix cars, and even make old cardboard boxes new again. Astronauts fixed the lunar dune buggy with it, and NASA sends some on every space mission they run, especially after fixing an air filter on the Apollo 13 mission. It's been used as a quick fix on oil wells and was used to keep World War II ammunition boxes dry. Some EMT handbooks describe ways to close up a chest wound with it. This item can be used to remove warts and could keep your windows from shattering in a storm. It's been said that if you can't fix it with this, you just aren't using enough. I'm, of course, talking about that silvery shape shifter - duct tape.

Duct tape has so many uses; don't you wish that everything was like that? I'm going to let you in on a little secret. There is something you might be using right now that has just as many uses. You use them at school, your parents use them at work, you find them online, and even that little picture telling you how much battery life you have left is one of these - they're graphs! Just like duct tape, graphs have thousands of uses! They can sway peoples' minds, be used to display parts of something bigger, and even show how something like temperature changes over the day. Can your fancy schmancy duct tape do that? I didn't think so.

So, what are graphs, and why do we use them? A graph is just a different way to look at data. Some people like reading charts, some like reading about numbers in a paragraph, others like looking at a picture representation, and that's where graphs come in. Graphs are a picture representation of numbers or data. It's as simple as that, but there are four main things about graphs that you need to remember before you can successfully make one.

First, don't start before you collect all your data. Second, graphs need to show data as a picture. Third, there's many types of graphs - each suited for a specific need. Using the proper graph to display data is crucial. Last, graphs need to have labels and titles that inform the reader. To help remember these four ideas, think of this mnemonic device: Don't Pick This Lemon. It's an acronym that you can help associate with the four ideas.

Look, the 'D' in 'Don't' is just like don't start without your data. The 'P' in 'Pick' is for pictures - we're making pictures out of data. The 'T' in 'This' stands for this graph type or that type - there's always a specific one to use. Finally, the 'L' in 'Lemons' is so you don't leave a sour face on anyone trying to figure out what your information is about on your graph. Remember, Don't Pick This Lemon! Let's look at these four ideas in more detail with some examples.

## Pie Graphs

As you already know, there's quite a variety of different graphs out there. You see them everywhere, but what's a person to do? There's so many graph types! There's pie graphs, box and whisker plots, bar graphs, stem and leaf plots, and line graphs. Not to mention Venn diagrams, word clouds, donut charts, info graphics, histograms, area charts... this list could go on for quite awhile.

Clear that jumbled pile out and let's focus on just a couple examples: pie graphs and line graphs. Remember, we're just looking for a new way to represent data as a picture. For example, you've probably seen something like this before; it's called a pie or a circle graph:

Just like duct tape has many specific uses, graphs have many specific uses, too.

A pie graph is useful in situations where there are parts of a whole or a percent of something. A good use of this type of graph would be a representation of what gases make up Earth's atmosphere, like we have here. These are all parts of a greater whole. Look at oxygen, it's red here. Since it makes up 21% of our atmosphere, it takes up 21% of this graph. Nitrogen is 78% of our atmosphere. See how that has a larger portion on the graph? There's also a tiny sliver of other gases in yellow which makes up the last 1%. If you were to add up all these numbers up, they would total 100%. A pie graph always needs add up to 100%.

Next, you need to have some written information on your graph explaining what's being shown. These are called labels, and every graph needs to have some type of label. Pie graphs need to have a way to identify what's being shown by each color. Usually, this is shown by something called a key or a legend, which is a small box in the corner explaining what each color represents. It should be simple and clear because too much info can make the graph hard to read.

Finally, all graphs need to have a title. The title needs to explain what's being represented by the graph. A good title, for this example, would be something like Earth's Atmospheric Gases or Gases Found in Earth's Atmosphere. These should be big and easy to read and placed somewhere out of the way of the chart's data.

Let's review our four main parts: Don't Pick This Lemon! After we collected data, we looked at a pie graph, which represented numbers by displaying different colors. This type of graph shows parts of a whole. Last, we looked at the title - the graph above is a great example of a pie graph.

Circle graphs are great for many things, but could you graph something like how the temperature changed at the beach on Tuesday with this type of graph? Actually, no. To make a graph with this type of data, a circle graph just won't work. But, not to fear! There are many graph types - we just need to pick the one that will represent these numbers better.

## Line Graphs

On one particular space walk, astronauts needed to get at a piece of material that was sticking out on the bottom of the space shuttle. If they couldn't get it with their gloved hands, they had a set of pliers. If that didn't work, they had made this new tool out of a hacksaw blade and, you guessed it, some duct tape. The point is, they knew they needed a better option if one way wasn't going to work. Now, we're in the same position. A pie graph just won't work for temperature.

A more appropriate graph to use in this situation would be a line graph. This type of graph is best used to show a trend or change over time. If the temperature starts out low and then gets warmer as the day progresses, a line graph would be a perfect way to show that data trend. Let's make this graph together. Here's what your data might look like:

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