Music sales: In recent years, sales of digital music ( downloads) have been increasing, while sales of physical units ( CDs, cassettes, and others) have been declining. The following table presents the number of units sold ( in millions) for both digital and physical music formats in each of the years 2007 through 2011.

a. Construct a time- series plot for digital sales. On the same axes, construct a time- series plot for physical sales.
b. Describe the trends in sales for digital and physical music formats.

Transcribed Image Text:

Physical Year 2007 2008 2009 2010 2011 Digital 1230.4 1450.7 1542.6 1471.9 1569.2 543.9 401.8 309.2 267.7 255.7 Source: Rocording Industry Asscciation of America