Have You Heard the Saying: “A Picture is Worth a Thousand Words”?
What is a Graph? Graphs and charts communicate information visually. For this reason, graphs are often used in newspapers, magazines and businesses around the world.
Why Use A Graph? Sometimes, complicated information is difficult to understand and needs an illustration. Other times, a graph or chart helps impress people by getting your point across quickly and visually.
How Do I Know Which Graph To Use?
Line Graph Line graphs can be used to show how something changes over time. Usually, the x-axis has numbers for the time period, and the y-axis has numbers for what is being measured. Line graphs can be used when you're plotting data that has peaks (ups) and valleys (downs), or that was collected in a short time period.
Bar graphs can be used to show how something changes over time or to compare items. Typically, the x-axis has numbers for the time period or what is being measured, and the y-axis has numbers for the amount of stuff being measured. Bar graphs are good when you're plotting data that spans many years (or days, weeks...), has really big changes from year to year (or day to day...), or when you are comparing things. Bar Graph
Pie Graph Pie charts can be used to show percentages of a whole, and represent percentages at a set point in time. They do not show changes over time.
Scatter Plots Scatter plots show how much one variable is affected by another. The relationship between two variables is called their correlation. A perfect positive correlation is given the value of 1. A perfect negative correlation is given the value of -1. If there is absolutely no correlation present the value given is 0. The closer the number is to 1 or -1, the stronger the correlation, or the stronger the relationship between the variables. The closer the number is to 0, the weaker the correlation.
Positive Correlation If the data points make a straight line going from the origin out to high x- and y-values, then the variables are said to have a positive correlation . An example of a situation where you might find a perfect positive correlation, as we have in the graph to the left, would be when you compare the total amount of money spent on tickets at the movie theater with the number of people who go. This means that every time that "x" number of people go, "y" amount of money is spent on tickets without variation.
Negative Correlation If the line goes from a high-value on the y-axis down to a high-value on the x-axis, the variables have a negative correlation. An example of a situation where you might find a perfect negative correlation, as in the graph to the left, would be if you were comparing the speed at which a car is going to the amount of time it takes to reach a destination. As the speed increases, the amount of time decreases.
No Correlation If one variable in not affected by the other, then the variables have no correlation. There is no relationship between the two variables.
Scatter Plots In-Between
Scatter Plots In-Between
Let's Graph!
Resources: http://www.mste.uiuc.edu/courses/ci330ms/youtsey/scatterinfo.html http://nces.ed.gov/nceskids/graphing/