This function estimates prevalence ratios (PRs) and bootstrap
confidence intervals using logistic models for conditional standardization.
The estimation of standard errors for PRs is obtained through use of bootstrapping.
Confidence intervals of (1-alpha)% for PRs are available for standard logistic regression
and for random-effects logistic models (Santos et al, 2008). The function
prLogisticBootCond allows estimation of PRs using conditional standardization procedure
(Wilcosky and Chambless, 1985).
any fitted model object from which fixed effects estimates can be extracted. The details of model specification are given below.
a required data frame containing the variables named in
scalar or vector specifying confidence level(s) for estimation. The default is
the number of bootstrap replicates. The default is
optional additional arguments. Currently none are used in any methods.
The fitted model object can be obtained using
glm() function for binary responses
when unit samples are independent. The
glmer() function should be used
for correlated binary responses. Only binary predictors are allowed. If categorization for predictors
is other than (0,1),
factor() should be considered.
Returns prevalence ratio and its 95% bootstrap confidence intervals for conditional standardization. Both normal and percentile bootstrap confidence intervals are presented.
Raydonal Ospina, Department of Statistics, Federal University of Pernambuco, Brazil
Leila D. Amorim, Department of Statistics, Federal University of Bahia, Brazil
Localio AR, Margolis DJ, Berlin JA (2007). Relative risks and confidence intervals were easily computed indirectly from multivariate logistic regression. Journal of Clinical Epidemiology, 60, 874-882.
Oliveira NF, Santana VS, Lopes AA (1997). Ratio of proportions and the use of the delta method for confidence interval estimation in logistic regression. Journal of Public Health, 31(1), 90-99.
Santos CAST et al (2008).
Estimating adjusted prevalence ratio in clustered cross-sectional epidemiological data.
BMC Medical Research Methodology, 8 (80). Available from
Wilcosky TC, Chambless LE (1985). A comparison of direct adjustment and regression adjustment of epidemiologic measures. Journal of Chronic Diseases, 34, 849-856.
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# Estimates from logistic regression with bootstrap confidence intervals - ## conditional standardization # Not run: # data("titanic", package = "prLogistic") # attach(titanic) # fit.logistic=glm(survived~ sex + pclass + embarked, family=binomial, # data = titanic) # prLogisticBootCond(fit.logistic, data = titanic) # End (Not run:) # Another way for fitting the same model: # Not run: # prLogisticBootCond(glm(survived~ sex + pclass + embarked, family=binomial, # data = titanic), data=titanic) # End (Not run:) ### For clustered data # Estimates from random-effects logistic regression ## with bootstrap confidence intervals - conditional standardization # Not run: # library(lme4) # data("Thailand", package = "prLogistic") # attach(Thailand) # ML = glmer(rgi ~ sex + pped + (1|schoolid), # family = binomial, data = Thailand) # prLogisticBootCond(ML, data = Thailand) # End (Not run:)
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