S.SY {TeachingSampling}

Systematic Sampling

Description

Draws a Systematic sample of size $n$ from a population of size $N$

Usage

S.SY(N, a)

Arguments

N

Population size

a

Number of groups dividing the population

Details

The selected sample is drawn according to a random start.

Value

The function returns a vector of size n. Each element of this vector indicates the unit that was selected.

Author(s)

Hugo Andres Gutierrez Rojas [e-mail]. The author acknowledges to Kristina Stodolova [e-mail] for valuable suggestions.

References

Madow, L.H. and Madow, W.G. (1944), On the theory of systematic sampling. Annals of Mathematical Statistics. 15, 1-24.
Sarndal, C-E. and Swensson, B. and Wretman, J. (1992), Model Assisted Survey Sampling. Springer.
Gutierrez, H. A. (2009), Estrategias de muestreo: Diseno de encuestas y estimacion de parametros. Editorial Universidad Santo Tomas.

See Also

E.SY

Examples

############
## Example 1
############
# Vector U contains the label of a population of size N=5
U <- c("Yves", "Ken", "Erik", "Sharon", "Leslie")
# The population of size N=5 is divided in a=2 groups
# Draws a Systematic sample. 
sam <- S.SY(5,2)
sam
# The selected sample is
U[sam]
# There are only two possible samples

############
## Example 2
############
# Uses the Lucy data to draw a Systematic sample
data(Lucy)
attach(Lucy)

N <- dim(Lucy)[1]
# The population is divided in 6 groups
# The selected sample
sam <- S.SY(N,6)
# The information about the units in the sample is stored in an object called data
data <- Lucy[sam,]
data
dim(data)