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The QLIM Procedure

Output to SAS Data Set

XBeta, Predicted, Residual

Xbeta is the structural part on the right-hand side of the model. Predicted value is the predicted dependent variable value. For censored variables, if the predicted value is outside the boundaries, it is reported as the closest boundary. For discrete variables, it is the level whose boundaries Xbeta falls between. Residual is defined only for continuous variables and is defined as


Error Standard Deviation

Error standard deviation is in the model. It varies only when the HETERO statement is used.

Marginal Effects

Marginal effect is defined as a contribution of one control variable to the response variable. For the binary choice model with two response categories, , , ; and ordinal response model with response categories, , define


The probability that the unobserved dependent variable is contained in the th category can be written as


The marginal effect of changes in the regressors on the probability of is then


where . In particular,


The marginal effects in the Box-Cox regression model are


The marginal effects in the truncated regression model are


where and .

The marginal effects in the censored regression model are


Inverse Mills Ratio, Expected and Conditionally Expected Values

Expected and conditionally expected values are computed only for continuous variables. The inverse Mills ratio is computed for censored or truncated continuous, binary discrete, and selection endogenous variables.

Let and be the lower boundary and upper boundary, respectively, for the . Define and . Then the inverse Mills ratio is defined as


for a continuous variable and defined as


for a binary discrete variable.

The expected value is the unconditional expectation of the dependent variable. For a censored variable, it is


For a left-censored variable (), this formula is


where .

For a right-censored variable (), this formula is


where .

For a noncensored variable, this formula is


The conditional expected value is the expectation given that the variable is inside the boundaries:



Probability applies only to discrete responses. It is the marginal probability that the discrete response is taking the value of the observation. If the PROBALL option is specified, then the probability for all of the possible responses of the discrete variables is computed.

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