Probit Analysis Options

Select the output to be generated initially in a probit analysis.

Display

Model	Details of the model that is fitted
Summary	Summary analysis of deviance
Correlations	Correlations between the parameter estimates
Estimates	Estimates of the parameters in the model
Fitted values	Table containing the values of the response variate, fitted values, standardized residuals and leverages
Effective doses	effective, or lethal, doses

The Confidence limit for effective doses (%) option lets you control the limit for the calculation of a confidence interval for the estimates of the effective (or lethal) dose. The limit is expressed as a percentage and must be in the range 0-100.

Dispersion parameter

Controls whether the dispersion parameter for the variance of the response is estimated from the residual mean square of the fitted model, or fixed at a given value. The dispersion parameter (Fix or Estimate) is used when calculating standard errors and standardized residuals.

Parameters to estimate separately for groups

Lets you select parameters you want to estimate separately for the different groups. You can include parameters for the Slope, Mortality and Immunity.

Effective (or lethal) dose

Specify the estimation of a effective dose (or lethal dose – LD). The LD50 value (that is the dose at which 50% of the population would respond) is always displayed as one of the parameters of the fitted line.

Base for backtransform of effective doses

This option is useful if the doses have been transformed to logarithms for the analysis. When the base of the logarithms (ten or e) is selected in the list, the backtransformed effective (or lethal) doses will be displayed as well.