computeN {CoRpower} | R Documentation |
If the power calculation is done at the study design stage, the function estimates the size and numbers of cases and controls in the target population of active treatment recipients observed to be at risk at the biomarker sampling timepoint.
computeN( Nrand, tau, taumax, VEtauToTaumax, VE0toTau, risk0, dropoutRisk, propCasesWithS )
Nrand |
the number of participants randomized to the active treatment group |
tau |
the biomarker sampling timepoint after randomization |
taumax |
the time after randomization marking the end of the follow-up period for the clinical endpoint |
VEtauToTaumax |
the treatment (vaccine) efficacy level between τ and τ_{max} |
VE0toTau |
the treatment (vaccine) efficacy between 0 and τ |
risk0 |
the overall placebo-group endpoint risk between τ and τ_{max} |
dropoutRisk |
the risk of participant dropout between 0 and τ_{max} |
propCasesWithS |
the proportion of observed cases with a measured biomarker response |
The function estimates design parameters that are required as input to computePower
. If the power calculation is done after the follow-up was completed, the estimates are replaced by the observed
counterparts for use as input parameters in computePower
.
The calculations include options to account for participant dropout by specifying dropoutRisk
as well as for incomplete sample storage by specifying propCasesWithS
.
The estimation procedure considers the standard survival analysis framework with failure and censoring times denoted by T and C, respectively, and makes the following assumptions:
T and C are independent.
T|Z=0 follows an exponential distribution with rate θ_t and C|Z=0 follows an exponential distribution with rate θ_c
RR_{τ-τ_{max}} := P(T <= τ_{max}|T> τ, Z=1)/P(T <= τ_{max}|T> τ, Z=0) is assumed to be equal to P(T <= t|T> τ, Z=1)/P(T <= t|T> τ, Z=0) for all t \in (τ,τ_{max}].
A list with the following components:
N
: the total estimated number of active treatment recipients observed to be at risk at τ
nCases
: the estimated number of clinical endpoint cases observed between τ and τ_{max} in the active treatment group
nControls
: the estimated number of controls observed to complete follow-up through τ_{max} endpoint-free in the active treatment group
nCasesWithS
: the estimated number of clinical endpoint cases observed between τ and τ_{max} in the active treatment group with an available biomarker response
Nrand = 4100 tau = 3.5 taumax = 24 VEtauToTaumax = 0.75 VE0toTau = 0.75/2 risk0 = 0.034 dropoutRisk = 0.1 propCasesWithS = 1 computeN(Nrand, tau, taumax, VEtauToTaumax, VE0toTau, risk0, dropoutRisk, propCasesWithS)