blm (version 2011.2.0)

logistic.rd: Estimate a risk difference between two subject types from a logistic regression model

Description

Point estimate and confidence interval for an absolute risk difference based on a logistic regression model of cohort binary data.

Usage

logistic.rd(type1, type2, type1.zero, type2.zero,fit, data, sig = 4, alpha = 0.05)

Arguments

type1

vector of covariate values for first probability estimate

type2

vector of covariate value for second probability estmate

type1.zero

vector of logical indicators for type1 covariates to be set to zero

type2.zero

vector of logical indicators for type2 covariates to be set to zero

fit

glm object for logistic regression

data

data frame on which the fit was based

sig

numeric number of significant digits for reported estimate

alpha

numeric value to specify the 100(1-alpha)% confidence interval for the risk difference

Value

• For probability of type1 - probability of type2, returns a list of est, se, lower, upper and CI.

Details

For covariates that are not given a fixed value of set to zero, the empirical distribution is determined from data and the marginal risk difference is computed by integrating over these factors.