factorial2x2
The goals of the factorial2x2
package are twofold: First, to provide
power calculations for a two-by-two factorial design in which the
effects of the two factors may be sub-additive. Power is provided for
the overall effect test for as well as the multiple testing procedures
described in Leifer, Troendle, Kolecki, and Follmann (2019). Second, to
analyze two-by-two factorial trial data which may include baseline
adjustment covariates. Further details are described in the factorial2x2
vignette.
Installation
You can install the released version of factorial2x2 from CRAN with:
install.packages("factorial2x2")
Example of a power calculation
We reproduce the power calculations for scenario 5 from Table 2 in
Leifer, Troendle, et al. using the fac2x2design
function.
n <- 4600 # total sample size
rateC <- 0.0445 # one year event rate in the control group
hrA <- 0.80 # simple A effect hazard ratio
hrB <- 0.80 # simple B effect hazard ratio
hrAB <- 0.72 # simple AB effect hazard ratio
mincens <- 4.0 # minimum censoring time in years
maxcens <- 8.4 # maximum censoring time in years
fac2x2design(n, rateC, hrA, hrB, hrAB, mincens, maxcens, dig = 2, alpha = 0.05)
$powerA
[1] 0.7182932 # power to detect the overall A effect at the two-sided 0.05 level
$power23.13
[1] 0.9290271 # power to detect the overall A or simple AB effects using the
# 2/3-1/3 procedure
$power13.13.13
[1] 0.9302084 # power to detect the overall A, simple A, or simple AB effects using
# the 1/3-1/3-1/3 procedure
$power12.12
[1] 0.9411688 # power to detect the simple A or simple AB effects using the
# 1/2-1/2 procedure
$events # expected number of events
[1] 954.8738
$evtprob # event probabilities for the C, A, B, and AB groups, respectively
probC probA probB probAB
0.2446365 0.2012540 0.2012540 0.1831806
References
Leifer, E.S., Troendle, J.F., Kolecki, A., Follmann, D. Joint testing of overall and simple effect for the two-by-two factorial design. 2019. Submitted.
Lin, D-Y., Gong, J., Gallo, P., et al. Simultaneous inference on treatment effects in survival studies with factorial designs. Biometrics. 2016; 72: 1078-1085.
Slud, E.V. Analysis of factorial survival experiments. Biometrics. 1994; 50: 25-38.