## Tuesday, December 18, 2012

### How to Make a Good Graph

There are some pretty basic guidelines when it comes to constructing graphs and it would be a good idea to make sure your kids know them too.

The first step is to determine which graph is appropriate for your data set. Will you make a bar graph? A line graph? A circle graph? Each type of graph presents information in a different way.

Line Graphs:
• Depict data when you want to see a relationship between two criteria- if you want to see if one variable increases or decreases as a result of a particular factor.
• To determine the relationship, you look at the line to see if the trend is up or down or neutral. It can be up and down as well. The direction of the slope will tell you something about the trend in the data.
• They can show data over a period of time.
• These graphs can accommodate more than one set of data- you can make the lines different colors and do some comparing.
Bar Graphs:
• Bar graphs are used to show sets of data.
• This is the graph to use when you have qualitative data to represent. Qualitative data is that which cannot be measured- so types of candy, books read, fish in the fish tank, etc. On the x axis you'd name the categories rather than making a scale of numbers.
• They can be made vertically or horizontally.
• Easily used in lots of subject areas because of the categories.
Circle Graphs:
• Represent a total amount or 100%
• The circle is divided into parts and works well when your data is broken down into percentages or fractions as they compare parts to the whole.
• This one is only used with you are graphing parts of data that make up a whole.

Every graph has to have a few things to be sure it is a well constructed graph and can be easily interpreted.

• Title- let the readers know what is depicted in the graph
• Label the x and y axis with the data set name and the units if there are any
• Evenly distribute the scale- make sure your graph begins at zero (most of the time) and counts away by a consistent amount. This is tricky sometimes to make sure you choose the right scale for your data set and sometimes is difficult for kids. A broken scale skews the data and can be misleading.
• Use a ruler! I would like to think this goes without saying, but neatly drawn lines is important in presentation and scale.
• Use color- graphs are visual representations and as such should be visually pleasing and eye catching.

Once your students are proficient at graph construction, you might consider ways to use technology to make a graph. The basics are still necessary so I think it's good practice for kids to be able to make a hand drawn graph first.

They can use a data spreadsheet (like Excel) to make their data charts and from there choose a graph they want to generate from that data.

Now that you've made a good graph, there are a lot more ways to manipulate data (in the good way) to draw conclusions and make confident statements about what we are studying. I'll be sure to share those soon!