Regression analysis periods

Methylmercuiy concentrations at site 3 A-15 in the Florida Everglades have shown distinct declining trends over the 8-year period from 1995 to 2003. A regression analysis of this data string shows a statistically significant (p = 0.048) decline rate of about 0.043 ng/L/year, and an overall decline of about 0.35 ng/L over the 8-year... 

Because a regression analysis of lethality data for squirrel monkeys and dogs showed an approximately linear response (n = 0.97 and 0.99, respectively, see Appendix B), the lethality threshold estimate (27.3 ppm) was linearly scaled (C1 xt=k) t° the AEGL time periods using the methods often Berge et al. (1986) (Appendix A). 

Two data sets of LC50 values for different time periods of exposure were analyzed using a linear regression analysis of the log-log transformation of a plot of C vs t to derive values of n for monomethylhydrazine. 

When data are lacking for desired exposure times, scaling across time may be based on the relationship between concentration and exposure duration (Cn xt=k) when a common end point is used (ten Berge et al. 1986). The end points for HCN are incapacitation and lethality. Regression analysis of the data of Sakurai (1989), using incapacitation concentrations for mice for the exposure durations of 5, 10, 20, and 30 min, results in a value for n of 1.6. Regression analysis of the incapacitation data of Purser et al. (1984) for monkeys for the time period of 8 to 19 min results in a value for n of 2.1 (Appendix A, Figure A-l). These studies were of relatively short duration. 

A typical time profile of the excited PMMA-Phe fluorescence intensity decay is shown in Figure 2. The MEK permeation commences at 24 sec. The SPR increases during the plasticization period until it becomes constant, the onset of the steady state. It is characterized by a linear relationship between the amount of solvent absorbed and time. It was determined from a linear regression analysis that the PMMA-Phe fluorescence intensity starts to deviate from linearity at 197 sec. This indicates a decrease in the SPR and/or the unquenched PMMA-Phe. The decrease in SPR is unexpected at this film thickness since the SPR in thicker PMMA-Phe films show no anomaly at 1 /tm. A more plausible explanation is the reduction in available PMMA-Phe, which is expected when the front end of the SCP reaches the substrate. 

A dramatic departure of ozone measurements from total oxidant measurements has b Mi reported for the Houston, Texas, area. Side-by-side measurements suggested that either method was a poor predictor of the other. Consideration was given to known interferences due to oxides of nitrogen, sulfur dioxide, or hydrogen sulfide, and the deviations still could not be accounted for. In the worst case, the ozone measurements exceeded the national ambient air quality standard for 3 h, and the potassium iodide instrument read less than 15 ppb for the 24-h period. Sulfur dioxide was measured at 0.01-0.04 ppm throughout the day. Even for a 1 1 molar influence of sulfur dioxide, this could not explain the low oxidant values. Regression analysis was carried out to support the conclusion that the ozone concentration is often much higher than the nonozone oxidant concentration. 

The result of the regression analysis to calculate the values of the two coefficients, a and b, of Eq. (59), nAt = a T, + b, holding for the induction period of the autocatalytic reaction of 0.4 g of collodion cotton confined in the closed cell and subjected to the isothermal storage test is presented in Table 22. 

Both the b and k values were estimated by regression analysis from the Taft steric constant Es and the Charton steric constant in an iterative procedure using 96 substituents. The k values are equal to 1.0 for the second period elements, except for the fluorine atom (k = 0.8) k = 1.2,1.3, and 1.7 for the third, fourth, and fifth period elements, respectively. 

Laboratories must update existing median values in several situations. Significant differences in values on the same patient specunens are common when using either a new lot of the reagents or reagents from a different manufacturer. In this situation, the relationship between the new and old methods can be established by regression analysis of values measured on the same patient specimens as described in the second method in the previous paragraph. If a periodic adjustment is required, the laboratory should carefully choose the characteristics of the population to be used (e.g.. 

The environmental rain data acquired at the site were compiled in Table 2 for each exposure period. Simple linear regression analysis was performed using each of the factors as the independent variable and the difference in corrosion (Aloss in Table 1) as the dependent variable. All of the regression coefficients were significant. The coefficients for the amount of rainfall were considere to be the most important, since delivery of SO, ... 

Three important findings are illustrated by the regression analysis of dicofol selection of T. urticae populations. First, factors other than dicofol selection pressure override the determination of population susceptibility to dicofol. Populations that had received 3, 4, or 5 dicofol treatments during the study period were just as susceptible as some populations that had received only one treatment. Clearly, factors mediating population susceptibility are strongly countering resistance development. 

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