SupProb {PracticalEquiDesign}

Superiority Probability

Description

Probability of selecting the more effective treatment as pr(median2 - median1 >= margin) + 0.5 * pr(abs(median2 - median1) < margin).

Usage

SupProb(
  cens_prop,
  n,
  med1 = NULL,
  shape1 = NULL,
  rate1 = NULL,
  med2 = NULL,
  shape2 = NULL,
  rate2 = NULL,
  info_reps = 50,
  margin = 0,
  use_exp_calc = TRUE
)

Arguments

cens_prop

Expected censoring proportion.

n

Sample size.

med1

Median for treatment arm 1, assuming shape1 = 1. Overwrites shape and rate if supplied.

shape1

Shape parameter for arm 1.

rate1

Rate parameter for arm 1.

med2

Median for treatment arm 2, assuming shape2 = 1. Overwrites shape and rate if supplied.

shape2

Shape parameter for arm 2.

rate2

Rate parameter for arm 2.

info_reps

Replicates used for estimating the observed information matrix.

margin

Margin of practical equivalence.

use_exp_calc

If both shape parameters are 1, should the calculations be performed assuming an exponential distribution for the time to event in each arm? Default is TRUE.

Value

Numeric equivalence probability.

Examples

# Calculation in the case of exponentials with no margin.
prob <- SupProb(
  cens_prop = 0.15,
  n = 100,
  med1 = 9,
  med2 = 12,
)

# Calculation in the case of exponentials with a 2 month margin.
# The probability should be lower than in the absence of a margin.
prob <- SupProb(
  cens_prop = 0.15,
  n = 100,
  med1 = 9,
  med2 = 12,
  margin = 2
)

# Calculation in the case of Weibulls with a 2 month margin.
prob <- SupProb(
  cens_prop = 0.15,
  n = 100,
  shape1 = 2.8,
  rate1 = 0.10,
  shape2 = 4.0,
  rate2 = 0.08,
  margin = 2
)