This library contains functions for calculating the
optimal two-stage sampling strategies in Reilly (1996).

The three functions here provide the optimal sampling 
strategies under different constraints:

  fixed.n       calculates the sampling fractions at the 
                second stage (given fixed first- and 
                second-stage sample sizes) which will 
		minimise the variance of a specified
                co-efficient in the regression model.

	
  budget	calculates the first-stage sample size 
                and the second stage sampling fractions
                that will maximise precision of a specified
                co-efficient subject to a given budget.

  precision     calculates the first-stage sample size 
                and the second stage sampling fractions
                that will minimise cost subject to
                a given precision for a specified co-efficient.

 two ilustrative datasets, cass1 and cass2 are also included
 in the package. Detailed help on each function and on the illustrative
 data sets can then be viewed be viewed by using help or ? 
 or the HTML help file system.

 Please read README.packages for details introduction	

 
Reilly M, Optimal Sampling Strategies for two-stage studies. 
         American Journal of Epidemiology, 143, 1, 92-100, 1996

Reilly,M and Pepe MS 1995. A mean score method for 
		missing and auxiliary covariate data in 
		regression models. Biometrika 82:299-314




 


