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Table 2 Slopes, intercepts and results of significance testing for the example data fitted to the probit-log(dose) regression models using the ML procedure (Excel), Polo-Plus and SPSS

From: Comparing lethal dose ratios using probit regression with arbitrary slopes

  Example Estimates Standard error (σ) z b
Excel Polo-Plus SPSS1a SPSS2a Excel Polo-Plus SPSS1a SPSS2a Excel Polo-Plus SPSS1a SPSS2a
β Rotenone 4.213 4.213 4.213 4.213 0.481 0.478 0.478 0.478 8.767 8.809 8.809 8.809
Deguelin 2.633 2.633 2.633 2.633 0.279 0.279 0.279 0.279 9.434 9.421 9.421 9.421
Mixture 2.533 2.533 2.533 2.533 0.269 0.272 0.272 0.272 9.400 9.320 9.320 9.320
Fairfax 2.598 2.598 2.598 2.598 0.352 0.353 0.353 0.353 7.370 7.369 7.369 7.369
Schaefer 2.812 2.812 2.812 2.812 0.281 0.273 0.273 0.273 9.999 10.282 10.282 10.282
Pixley c 2.982 2.917 2.915 4.897 0.401 0.402 0.401 1.200 9.999 7.248 7.264 4.080
BugRes 1.730 1.551 1.545 1.703 0.270 0.252 0.229 0.532 6.402 6.148 6.736 3.202
BugLab 5.541 5.461 4.941 3.631 0.960 1.062 0.948 0.716 5.771 5.142 5.215 5.071
α Rotenone −2.887 −2.887 −2.887 −2.887 0.351 0.350 0.350 0.350 −8.225 −8.247 −8.247 −8.247
Deguelin −2.622 −2.622 −2.622 −2.622 0.342 0.339 0.339 0.339 −7.670 −7.743 −7.743 −7.743
Mixture −2.036 − 2.036 − 2.036 − 2.036 0.271 0.272 0.272 0.272 −7.519 −7.491 −7.491 −7.491
Fairfax −1.603 −1.603 −1.603 −1.603 0.250 0.249 0.249 0.249 −6.413 −6.435 −6.435 −6.435
Schaefer −1.622 −1.622 −1.622 −1.622 0.190 0.186 0.186 0.186 −8.530 −8.728 −8.728 − 8.728
Pixley c −3.666 −3.556 −3.552 −6.778 0.531 0.529 0.527 1.832 −6.903 −6.719 −6.741 −3.699
BugRes −2.387 −2.064 −2.053 − 2.338 0.384 0.367 0.315 0.908 −6.218 −5.618 − 6.512 −2.575
BugLab −5.690 −5.587 −4.935 −3.640 1.028 1.141 0.997 0.754 −5.535 −4.897 −4.951 −4.826
  1. aSPSS includes the natural responses proportion (C) by two methods: 1, inputting the value of C; and 2, calculating the corrected p from the data. The d.f. = k − 2 in method 1, while it was k-3 in method 2
  2. bPolo-Plus used the t-ratio to test the significance of the linear regression. The significance criterion for the t-ratio (α = 0.05) was 1.96 (t-distribution with d.f. = ∞). This significance level was identical to that of the z test
  3. cBold items indicated the data sets included natural responses