| OCR Text |
Show PMX-1061 Page 9 of 13 The test endpoints will be based on the adverse effects of selenate on D. viridis cell growth. Algal growth data derived from the chronic tests will be used to statistically 'estimate the EC50, No Observed Effect Concentration (NOEC) and Lowest Observed Effect Concentration (LOEC) of selenate after 96 hours of exposure. Statistical analyses will be conducted using the Statistical Package for the Social Sciences (SPSS, Norusis, 1993) in accordance with procedures described in U.S. EPA (1994) and EU (1992). Growth rate and total area under the curve will be calculated for each replicate and summary statistics for each time period calculated. The effects of extreme observations ( outliers) will be investigated by eliminating those values, one by one, from the data set, rerunning analyses, and reporting results without outliers. Outliers will be defined as data values with Studentized Residuals greater than two. Growth rate between each consecutive time period will be calculated using the logistic growth equation: for i 1, = where ... , n growth rate between time i and time j = = .timei number of cells at time i for replicate j = Total area under the curve (increase in number of cells) from hour 0 through the final time period (n) will be calculated as: II A). = t1 *(N.. 'J - N .)/2 OJ + r L..J (tII - T11- I) * (N 11- I' J + N . nJ 2 *N .)/2 OJ ;=1 where A = area under the t, = timei NiJ = number of cells at time i for replicate j growth curve for replicate j A statistical computer package will be used to estimate the EC50 values and the 95 % confidence intervals. analysis, These programs estimate EC values using one of three statistical methods: probit moving average method, or binomial probability. The method selected will be |
