PracTools (version 1.6)

nCont: Compute a simple random sample size for an estimated mean

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

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

Value

numeric sample size

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

Author

Richard Valliant, Jill A. Dever, Frauke Kreuter

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.

References

Valliant, R., Dever, J., Kreuter, F. (2018, chap. 3). Practical Tools for Designing and Weighting Survey Samples, 2nd edition. New York: Springer.

See Also

nLogOdds, nProp, nPropMoe, nWilson

Examples

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)