Represents the issue of selection bias in a clinical trial.
selBias(type, eta, method, alpha = 0.05)
character string, should be one of "CS"
, "CS2"
or "DS"
, see
Details.
numeric specifying the magnitude of selection bias.
character string, should be one of "sim"
or "exact"
, see
Details.
significance level.
S4
object of class selBias
, a formal representation of the
issue of selection bias in a clinical trial.
Selection bias can be an issue in the design of a clinical trial. The
selBias
function is a constructor function
for an S4 object of the class selBias
representing the issue of
third order selection bias in a clinical trial. It supports two possible modes,
method="sim"
and method="exact"
. This representation is
particularly useful in interaction with the assess
function.
method="sim"
Represents the simulated type-I-error rate given
the level alpha
, the selection effect eta
and the biasing
strategy type
. When calling assess
for a selBias
object
with method="sim"
, one test decision is computed for each sequence of
randSeq
. The type-I-error rate (power) is the proportion of falsely
(correctly) rejected null hypotheses.
method="exact"
Represents the exact type-I-error proabability
given the level alpha
, the selection effect eta
and the
biasing strategy type
. When calling assess
for a selBias
object with method="exact"
, the exact p-value of each
randomization sequence is computed. So far, this is only supported for
normal endpoints. Then the type-I-error probability is
the sum of the corresponding quantiles of the doubly noncentral t-distribution.
D. Blackwell and J.L. Hodges Jr. (1957) Design for the control of selection bias. Annals of Mathematical Statistics, 25, 449-60.
M. Proschan (1994) Influence of selection bias on the type-I-error rate under random permuted block designs. Statistica Sinica, 4, 219-31.
Compute exact or simulated type-I-error: assess
.
Other issues: chronBias
,
combineBias
, corGuess
,
imbal
, issue
,
setPower