Fundamentals of Math

Fundamentals of Mathematics

Lastly, good graphs should match the data it is portraying. More on this to come, but in a nut-shell –

• Line graphs are used for data that varies continuously, but the relationship between the two variables is more complex (think lots of ups and downs). • Bar graphs can be used to plot categorical data (things we count/observe but cannot measure) that does not vary continuously. • Pie charts are best used to represent percentages or parts of a whole. • Scatter plots with best-fit lines are used for data that varies continuously and is linear. 6.2 Line Graph Line graphs are used to show how information is connected in some way (such as change over time). It is made up of two axes, and data are plotted as order pairs on the graph and then connected using a line. To create a line graph, begin by drawing the -axis (independent variable) and -axes (dependent variable) on the page. Be sure to add titles to both axes and label your graph. Each axis should be labeled with the name of the numeric system, as well as the measurements being used. For example, you may mark the -axis with "Time (Days)", indicating that each number written on the axis is a number of days. Divide each axis evenly into applicable increments.

Add your data. Data for a line graph is usually contained in a two-column table corresponding to the - and -axes. Once you've plotted your points, connect each subsequent point using a straight edge.

Example 6.2

Revenue in CD’s sold in the U.S.A. from 2000 to 2009 Data taken from RIAA – U.S. Sales Database (https://www.riaa.com/u-s-sales-database/ )

Year

2000 2001 2002 2003 2004 2005 2006 2007 2008 2009

$ Earned in Millions 13.2 12.9 12.0 11.2 11.4 10.5

9.4

7.5

5.5

4.3

After studying the graph, we can deduce a few things. One in general, revenue from CD Sales is on a downward trend. The revenue earned in 2009 is less than half of what it was in 2000. Judging by the current dataset, it wouldn't be farfetched to consider CD sales to be almost non-existent by 2020.

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