List all the data you have on a sheet of paper. For example, if you are collecting data to see how much people study each night, write down the number of hours each teenager reports studying. You will have some duplicates; for example, if five teenagers say they study two hours a night, write the number "2" five separate times.
Examine the set of data to see the highest and lowest number. In the case of hours spent studying, assume the lowest number can be 0 and the highest 6.
Group the data into classes between the lowest and highest numbers. For example, if you have data between 0 and 6, group it into three sets: 0-2, 3-4 and 5-6. List these classes on the paper.
Tally up the total number of teenagers who belong in each class. For example, five teenagers study two hours nightly, two study one hour and three study 0 hours. The total number of teenagers who fit into the first class, 0-2 hours, is 10, so the frequency for that class is 10. Repeat with the remaining classes.
Draw an X and Y axis on the paper. X is the horizontal axis while Y is the vertical. Mark the frequencies on the vertical (Y) axis and the classes, or hours spent studying, on the horizontal (X) axis.
Plot a point at 10 on the Y axis and 0 on the X axis, as well as at (1,10) and (2,10) to show the first class and frequency of data. Draw a vertical line down to 0 on the Y axis and make a bar. Repeat with the remaining classes. When finished, you'll have a bar graph showing the frequency of each data class. If you look at the size of each bar, you can determine whether the data is skewed. For example, if 10 students study 0-2 hours nightly and only two students study 5-6 hours, you can say that the data is skewed to the left. If 10 students study 0-2 hours, as well as 3-4 hours and 5-6 hours, then the data is symmetrical.