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<br />. <br /> <br />. <br /> <br />18 <br /> <br />Young-of-the-year Production (based on annual CPE data) <br /> <br />CPE data have been collected for yay from 1982 through 1997. Before 1993. <br />only geometric means of each year's data were recorded. From 1993 through <br />1997. Standard Error (SE) values also were computed for yay data (Table 9, <br />Figure 9). To establish a baseline for yay, an arithmetic mean, x~0.382733. <br />(solid horizontal line in Figure 9) and SE=iO.252791 (dashed horizontal lines <br />in Figure 9), were calculated from the annual geometric means of all existing <br />CPE data, The upper dashed line. x+SE~0.635524, is the threshold value used <br />to determine a positive, negative. or neutral response. based on the frequency <br />with which yay CPE exceeds this value. <br /> <br />Three different indices were evaluated to compare the simulated data in the <br />examples below with the baseline data: a cumulative average based on the <br />number of years the threshold value (baseline) is exceeded divided by the <br />total number of years to date; a 5-year rolling average based on the number of <br />years the threshold value is exceeded in any 5 consecutive years; and a 10- <br />year rolling average based on the number of years the threshold value is <br />exceeded in any 10 consecutive years (Tables 10-12). <br /> <br />yay are considered to exhibit a positive response whenever CPE-SE exceeds the <br />threshold at least once in 5 consecutive years (20 percent) on average <br />(e.g" 2 in 10 years. 3 in 15 years. etc.)(Table 10. Figure 10). In this <br />example. the results are unambiguous. Beginning in 1999. all three indices <br />show a positive response (i .e.. threshold exceedance frequency> 20 percent). <br /> <br />If yay CPE-SE does not exceed 0.635524 at least once in 10 years (10 percent), <br />a negative response would result (Table 11, Figure II). However. a negative <br />yay response would not be indicated until 10 consecutive years of threshold <br />nonexceedance had elapsed, In this case. the 10-year rolling average appears <br />to provide the best index. because it would indicate a negative yay response <br />only if CPE-SE fails to exceed the threshold at least once during any 10-year <br />period. <br /> <br />While the negative example above is unambiguous. the neutral response scenario <br />could be interpreted several different ways. depending on which index is used <br />(Table 12, Figure 12). Based on the above scenarios. a neutral response would <br />result if values of CPE-SE exceed 0.635524 at least once in 10 years. but less <br />than once in 5 years (e.g., 2 in 15 years). In the neutral example, however. <br />only 1 year in 14 (7 percent) exceeds the threshold value. The cumulative <br />average exceeds 10 percent only 5 out of 14 years, while the 5-year rolling <br />average exceeds 20 percent in 5 of 10 years, but is 0 percent during the other <br />