Confidence Interval Approach for the Number of Subjects Required for a Study of Interobserver Agreement with a Binary Outcome

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Description

This function provides detailed sample size estimation information to determine the number of subjects required using the confidence interval perspective to sample size estimation for κ. This version assumes that the outcome has two categories.

Usage

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CIBinary(kappa0, kappaL, kappaU=NA, props, raters=2, alpha=0.05)

Arguments

kappa0

The preliminary value of κ.

kappaL

The desired expected lower bound for a two-sided 100(1 - α) % confidence interval for kappa. Alternatively, if kappaU is set to NA, the procedure produces the number of required subjects for a one-sided confidence interval.

kappaU

The desired expected upper confidence limit for kappa.

props

The anticipated prevalence of the desired trait. Note that specifying props as either a single value, or two values that sum to one provides the same result.

raters

The number of raters that are available. This function allows between 2 and 6 raters.

alpha

The desired type I error rate.

Details

This function provides detailed sample size estimation computation for studies of interobserver agreement with a binary outcome. This function employs the confidence interval perspective, determining the correct sample size that provides the specified expected confidence limits. Sample size estimation is based on the precision of the estimate, instead of a simple hypothesis testing perspective. Note that a warning message is provided if any of the expected cell counts are less than 5.

Value

N

The calculated sample size.

kappa0

The specified anticipated value of κ.

kappaL

The specified expected lower limit.

kappaU

The specified expected upper limit.

props

The anticipated proportion of individuals with the outcome.

raters

The number of raters.

alpha

The desired type I error rate.

ChiCrit

The critical value that is required for sample size estimation. It is typically not required and is not displayed in the summary output.

Author(s)

Michael Rotondi, mrotondi@uwo.ca

References

Donner A, Rotondi MA. (2010). Sample Size Requirements for Interval Estimation of the Kappa Statistic for Interobserver Agreement Studies with a Binary Outcome and Multiple Raters. International Journal of Biostatistics 6:31.

Altaye M, Donner A, Klar N. (2001). Procedures for Assessing Interobserver Agreement among Multiple Raters. Biometrics 57:584-588.

Donner A. (1999). Sample Size Requirements for Interval Estimation of the Intraclass Kappa Statistic. Communication in Statistics 28:415-429.

Bartfay E, Donner A. (2001). Statistical Inferences for Interobserver Agreement Studies with Nominal Outcome Data. The Statistician 50:135-146.

Donner A, Eliasziw M. (1987) Sample size requirements for reliability studies. Statistics in Medicine 6:441-448.

See Also

PowerBinary

Examples

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## Not run: Suppose an investigator would like to determine the required sample size to test
kappa0=0.4 with precision of 0.1 on each side, in a study of interobserver agreement. 
Further suppose that the prevalence of the trait of interest is 0.30.
## End(Not run)
CIBinary(kappa0=0.4, kappaL=0.3, kappaU=0.5, props=0.30, alpha=0.05);