Fundamentals of Math

Fundamentals of Mathematics

6.3 Pie Charts Pie charts are used to show relative sizes of data. It consists of a circle divided into sectors that each represent a proportion of the whole. Each sector (or "slice of pie") represents a smaller part of the whole, but when all the sectors are added together, you get the total sum ("the entire pie"). To create a pie chart from scratch, begin by summing your total number of observations. Next, divide each category total by the grand total and multiply by 100 to get a percentage. Then figure out how many degrees each section of the circle will be by multiply 360 ° by each percentage. Use these angle measurements to divvy up the circle.

Example 6.3

Directions: Using the data from Table 6.1 create a pie chart that represents what percentage of patients received each type of drug.

No. of Patients Receiving Each Drug in the Study

Drug

A

C

X

Y Grand Total

No. of Patients 91 16 54 39

200

From this graph, we can interpret a majority of patients received drug Y, followed by drug X, then drug A. Finally, the fewest number received drug C.

6.4 Bar Graphs Bar graphs display how data relates to one another using bars of different heights (or lengths). Data is drawn on horizontal or vertical axes, and the height (or length) of the bars is proportionate to the frequency in the dataset. Note: Bar graphs are used exclusively for categorical data (values are collected in groups or categories). The graph itself is made up of an and -axis. Usually, the -axis contains the categories of what is being measured, and the -axis contains the counts of what was measured. Some bar graphs will even contain multiple counts to help readers visualize how items compare next to one another. To create your graph, begin by drawing the vertical and horizontal axes (don't forget to label them). Next, write your categories along the -axis ( for horizontal bar graphs invert the axes in the following set of directions ) to show where the bars will go. Then using your data, determine the scale for your -axis. Make sure your scale shows the largest and smallest counts in your dataset. Begin at zero and count up based on your scale. Finally, draw a rectangle (a bar) above each category that has a height equal to its overall count.

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