Blinded estimation of average hazard ratio

Based on blinded data and assumed hazard ratios in different intervals, compute a blinded estimate of average hazard ratio (AHR) and corresponding estimate of statistical information. This function is intended for use in computing futility bounds based on spending assuming the input hazard ratio (hr) values for intervals specified here.

Usage

ahr_blinded(
  surv = survival::Surv(time = simtrial::ex1_delayed_effect$month, event =
    simtrial::ex1_delayed_effect$evntd),
  intervals = c(3, Inf),
  hr = c(1, 0.6),
  ratio = 1
)

Arguments

surv

Input survival object (see survival::Surv()); note that only 0 = censored, 1 = event for survival::Surv().

intervals

Vector containing positive values indicating interval lengths where the exponential rates are assumed. Note that a final infinite interval is added if any events occur after the final interval specified.

hr

Vector of hazard ratios assumed for each interval.

ratio

Ratio of experimental to control randomization.

Value

A tibble with one row containing

• ahr - Blinded average hazard ratio based on assumed period-specific hazard ratios input in fail_rate and observed events in the corresponding intervals.

• event - Total observed number of events.

• info0 - Information under related null hypothesis.

• theta - Natural parameter for group sequential design representing expected incremental drift at all analyses.

Specification

The contents of this section are shown in PDF user manual only.

Examples

ahr_blinded(
  surv = survival::Surv(
    time = simtrial::ex2_delayed_effect$month,
    event = simtrial::ex2_delayed_effect$evntd
  ),
  intervals = c(4, 100),
  hr = c(1, .55),
  ratio = 1
)
#> # A tibble: 1 × 4
#>   event   ahr theta info0
#>   <dbl> <dbl> <dbl> <dbl>
#> 1   228 0.826 0.191    57