# nCont: Compute a simple random sample size for an estimated mean In PracTools: Tools for Designing and Weighting Survey Samples

## Description

Compute a simple random sample size using either a target coefficient of variation, CV_0, or target variance, V_0, for an estimated mean.

## Usage

 1 nCont(CV0=NULL, V0=NULL, S2=NULL, ybarU=NULL, N=Inf, CVpop=NULL) 

## Arguments

 CV0 target value of coefficient of variation of \bar{y_s} V0 target value of variance of \bar{y_s} S2 unit (population) variance ybarU population mean of target variable N number of units in finite population CVpop unit (population) coefficient of variation

## Details

If CV_0 is the desired target, then the unit CV, CVpop, or the population mean and variance, ybarU and S2, must also be provided. If V_0 is the constrained value, then S2 must be also be included in the function call.

## Value

numeric sample size

## Author(s)

Richard Valliant, Jill A. Dever, Frauke Kreuter

## References

Valliant, R., Dever, J., Kreuter, F. (2013, chap. 3). Practical Tools for Designing and Weighting Survey Samples. New York: Springer.

nLogOdds, nProp, nPropMoe, nWilson
  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 nCont(CV0=0.05, CVpop=2) nCont(CV0=0.05, CVpop=2, N=500) nCont(CV0=0.10/1.645, CVpop=1) # Compute sample size for a ratio estimator in smho98 population # Identify large units to select with certainty first data(smho98) cert <- smho98[,"BEDS"] > 2000 tmp <- smho98[!cert, ] tmp <- tmp[tmp[, "BEDS"] > 0, ] x <- tmp[,"BEDS"] y <- tmp[, "EXPTOTAL"] m <- lm(y ~ 0 + x, weights = 1/x) ybarU <- mean(y) S2R <- sum(m\$residuals^2/(length(x)-1)) nCont(CV0=0.15, S2=S2R, ybarU=ybarU)