Figure 2.11 is titled "Numbers (in Thousands) of Daily or Almost Daily Marijuana Users in the Past Year and Past Month among Youths Aged 12 to 17: 2002 and 2003." It is a bar graph, with the following note below the graph: "Statistically significant differences (at 0.05 level) between 2002 and 2003 are denoted by '+.'" The horizontal axis represents selected frequencies of marijuana use, and the vertical axis represents the numbers of users, in thousands. There are two categories of frequency of marijuana use: Used on 300 or More Days in the Past Year, and Used on 20 or More Days in the Past Month. Within each usage category there is a bar for 2002 and a bar for 2003. For each marijuana use frequency category and year combination, the number of users among persons aged 12 to 17 is as follows:
The number of youths who used marijuana on 300 or more days in the past year was 358,000 in 2002 and 282,000 in 2003. This is a significant difference at the 0.05 level.
The number of youths who used marijuana on 20 or more days in the past month was 603,000 in 2002 and 482,000 in 2003. This is a significant difference at the 0.05 level.