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.