Graphs: Are You Plotting Something?

Lesson Plan - Get It!

Audio:

Oh no! Maybe your phone bill has been increasing.

• Or has it been decreasing?

You can graph your phone bill charges on bar graphs, line graphs, and histograms. This will help you visually see if your bills are increasing or decreasing over time.

Each type of graph is different.

A bar graph presents data with rectangular bars with heights equal to the values that they represent.

For example, this bar graph represents Eden's cell phone bill over several months:

Each bar represents the bill amount for that month. The first J is for January, and the bar goes up to $60:

Then, the F is for February, and the bar goes to $50, and so on for each month:

• Does the amount of Eden's cell phone bills increase or decrease?

If you look at the top of each graph and then look at the next one, you can see if the amount of the cell phone bill increased.

Looking at the bar graph, we see that the charge decreased, then increased, and decreased again.

Over the last three months, we see a pattern that shows that the amount of Eden's cell phone bill charges has decreased.

A line graph is used to show information that changes over time. We plot line graphs using several points connected by straight lines.

This line graph represents the same cell phone bill as in the bar graph:

Just like the bar graph, J is for January, and the bill is at $60. But this time, it is a dot at $60:

The F is for February, and the dot is at $50, and so on for the rest of the months:

Looking at the line graph, we see that the charge decreased, then increased, and decreased again.

Over the last three months, we see a pattern that shows that the amount of the cell phone bill charges has decreased, just as the bar graph showed.

A histogram uses bars of different heights. Each bar groups numbers into ranges.

We can represent Eden's cell phone bills with a histogram; however, it will not show us whether her cell phone bill is increasing or decreasing.

• Why not?

The histogram represents the same cell phone bills as the bar graph and line graph:

The bar graph and line graph represented each month individually. A histogram shows the data differently, in groups.

There are no rectangles above $10, $20, or $30. This is because no month's bill was that amount.

However, the rectangle above $40 goes to 1 because one month had a bill that was $40:

The rectangle above $50 goes to 2 because there were two months when the cell phone bills were $50. The remaining sections of the histogram represent the other charges for bills:

The histogram represents the cell phone bill charges over several months, but it is not a good representation to determine if the bills are increasing or decreasing.

• Ready to put all this into practice?

Then head over to the Got It? section!