DTR (version 1.7)

contrast_wald: Function to compare dynamic treatment regimes (DTRs) using Wald-type tests

Description

This function compares the survival estimates at specific time point among dynamic treatment regimes (DTRs) using the Wald-type tests.

Usage

contrast_wald(est, t = quantile(est$time, 0.75))

Arguments

est

the result of a call to the LDTestimate function or WRSEestimate function

t

a time point of interest. For example, t=5 for the comparisons of survival estimates at 5 years among DTRs. Default t is set to be the 75th percentile of the observed time (i.e. 75th percentile of U).

Value

The function returns a data frame with four columns: H0, test statistic, df, and p.

H0

the null hypotheses being tested, for example, H0 (t=3) if the comparisons are made at t=3

test statistic

the calculated chi-square test statistic

df

the degree of freedom

p

the resulting p-value

Details

Two different comparisons are performed: 1) An overall comparison H0: A1B1=A1B2=A2B1=A2B2 2) Pairwise comparisons including H0: A1B1=A1B2, H0: A1B1=A2B1, H0: A1B1=A2B2, H0: A1B2=A2B1, H0: A1B2=A2B2, and H0: A2B1=A2B2

References

Lunceford JK, Davidian M, Tsiatis AA: Estimation of survival distributions of treatment policies in two-stage randomization designs in clinical trials. Biometrics 58:48-57, 2002 Guo X, Tsiatis AA: A weighted risk set estimator for survival distributions in two-stage randomization designs with censored survival data. Int. J. Biostatistics 1:1-15, 2005

See Also

LDTestimate, WRSEestimate, DTR.object

Examples

## Not run: 
# # LDT estimates
# data("LDTdata")
# est <- LDTestimate(data=LDTdata)
# contrast_wald(est, t=1)
# 
# # WRSE estimates
# data("WRSEdata")
# est <- WRSEestimate(data=WRSEdata)
# contrast_wald(est, t=300)
# ## End(Not run)