CI4Cats: Confidence Interval Approach for the Number of Subjects...

In kappaSize: Sample Size Estimation Functions for Studies of Interobserver Agreement

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 four categories.

Usage

CI4Cats(kappa0, kappaL, kappaU=NA, props, raters=2, alpha=0.05)

Arguments

kappa0	The preliminary (anticipated) value of κ.
kappaL	The desired expected lower bound for a two-sided 100(1 - α) % confidence interval for κ. 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 κ.
props	The anticipated prevalence of the desired trait. Note that the elements of the four element vector must be non-negative and sum to one.
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 four outcomes. 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 proportions of individuals with the outcomes of interest.
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, [e-mail]

References

Rotondi MA, Donner A. (2012). A Confidence Interval Approach to Sample Size Estimation for Interobserver Agreement Studies with Multiple Raters and Outcomes. Journal of Clinical Epidemiology, 65:778-784.

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

Power4Cats

Examples

## 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 traits are 0.30, 0.2, 0.2, 0.3.
## End(Not run)

CI4Cats(kappa0=0.4, kappaL=0.3, kappaU=0.5, props=c(0.30, 0.2, 0.2, 0.3), alpha=0.05);

kappaSize documentation built on May 1, 2019, 9:21 p.m.