RJafroc (version 1.2.0)

SsSampleSizeKGivenJ: Number of cases, for specified number of readers, to achieve desired power

Description

Number of cases to achieve the desired power, for specified number of readers J, and specified DBMH or ORH analysis method

Usage

SsSampleSizeKGivenJ(dataset, J, alpha = 0.05, effectSize = NULL,
  desiredPower = 0.8, option = "ALL", method = "DBMH", ...)

Arguments

dataset

The pilot ROC dataset to be used to extrapolate to the pivotal study. If missing, then variance components and effectSize must be passed as additional parameters.

J

The number of readers in the pivotal study.

alpha

The significance level of the study, default is 0.05.

effectSize

The effect size to be used in the pivotal study, default value is NULL.

desiredPower

The desired statistical power, default is 0.8.

option

Desired generalization, "RRRC", "FRRC", "RRFC" or "ALL" (the default).

method

"DBMH" (default) or "ORH".

...

Other parameters, OR or DBM variance components, passed internally, see details

Value

A list of two elements:

K

The minimum number of cases K in the pivotal study to just achieve the desired statistical power.

power

The predicted statistical power.

Details

Other parameters ... are reserved for internal use. The default effectSize uses the observed effect size in the pilot study. A numeric value over-rides the default value.

References

Hillis SL, Obuchowski NA, Berbaum KS (2011) Power Estimation for Multireader ROC Methods: An Updated and Unified Approach, Acad Radiol, 18, 129--142.

Hillis SL, Obuchowski NA, Schartz KM, Berbaum KS (2005) A comparison of the Dorfman-Berbaum-Metz and Obuchowski-Rockette methods for receiver operating characteristic (ROC) data, Statistics in Medicine, 24:10, 1579--607.

Examples

# NOT RUN {
## An example using the DBM method
SsSampleSizeKGivenJ(dataset02, J = 6, method = "DBMH")

## An example using the OR method
SsSampleSizeKGivenJ(dataset02, J = 6, method = "ORH")


# }
# NOT RUN {
for (J in 6:10) {
 ret <- SsSampleSizeKGivenJ(dataset02, J = J, option = "RRRC") 
 message("# of readers = ", J, " estimated # of cases = ", ret$K, ", predicted power = ",
    signif(ret$powerRRRC,3), "\n")
}
# }
# NOT RUN {
# }