Overall Prediction Accuracy at the State Level, Based on State Averages 1987-2005
Over the 19-year period (1987-2005), 245 State-level predictions of SPB infestation trend and population level were made by averaging the mean SPB per trap per day and percent SPB for all locations monitored within each State for each year of participation in the Southwide survey. To determine overall accuracy of predictions at the State level, a 9 by 9 matrix was prepared to compare predicted versus actual infestation trends and population levels for every possible trend or level category (declining to low level, declining to moderate level, declining to high level, static at low level, static at moderate level, static at high level, increasing to low level, increasing to moderate level, increasing to high or outbreak level). Overall, the infestation trend and population level were both predicted accurately in 57 percent of the cases (140 of 245). The category of static or low was correctly predicted 85 percent of the time (45 of 53 cases) whereas the declining or low category was correctly predicted 73 percent of the time (60 of 82 cases). These two categories were the most common situations experienced across the South from 1987 to 2005, occurring in 55 percent of the total cases.
A 3 by 3 matrix was used to evaluate predicted and actual SPB trends alone (Figure 1). SPB infestations that increased by more than 25 percent from the previous year (increasing trend) occurred in 30 percent of the 245 cases and were correctly predicted 62 percent of the time. Those that declined by at least 25 percent from the previous year occurred in 43 percent of the cases and were correctly predicted 80 percent of the time. Static infestation trends (≤ 25 percent change from previous year) occurred in 27 percent of the cases and were correctly predicted 76 percent of the time.
A separate matrix was used for SPB population levels (Figure 2). Low SPB population levels occurred in 64 percent of the 245 cases and were correctly predicted 85 percent of the time. Moderate levels occurred in 26 percent of the cases and were correctly predicted 54 percent of the time. In contrast, SPB populations reached high levels in 10 percent of the cases but were correctly predicted to do so only 32 percent of the time. However, 88 percent of those States that experienced high SPB infestation levels were predicted to have at least moderate levels. Major errors in both infestation trend and population level predictions occurred in only 3 percent of the cases. Major errors (those cases within red boxes in Figures 1 and 2) in trend predictions alone occurred in 11 percent of the cases (28 of 245 cases) whereas major errors in population level predictions alone occurred in only 2 percent of the cases (5 of 245 cases).
Encyclopedia ID: p3294
