ss4dmH {samplesize4surveys}

The required sample size for testing a null hyphotesis for a single difference of proportions

Description

This function returns the minimum sample size required for testing a null hyphotesis regarding a single difference of proportions.

Usage

ss4dmH(
  N,
  mu1,
  mu2,
  sigma1,
  sigma2,
  D,
  DEFF = 1,
  conf = 0.95,
  power = 0.8,
  T = 0,
  R = 1,
  plot = FALSE
)

Arguments

N

The maximun population size between the groups (strata) that we want to compare.

mu1

The value of the estimated mean of the variable of interes for the first population.

mu2

The value of the estimated mean of the variable of interes for the second population.

sigma1

The value of the estimated variance of the variable of interes for the first population.

sigma2

The value of the estimated mean of a variable of interes for the second population.

D

The minimun effect to test.

DEFF

The design effect of the sample design. By default DEFF = 1, which corresponds to a simple random sampling design.

conf

The statistical confidence. By default conf = 0.95.

power

The statistical power. By default power = 0.80.

T

The overlap between waves. By default T = 0.

R

The correlation between waves. By default R = 1.

plot

Optionally plot the effect against the sample size.

Details

We assume that it is of interest to test the following set of hyphotesis:

H_0: mu_1 - mu_2 = 0 \ \ \ \ vs. \ \ \ \ H_a: mu_1 - mu_2 = D \neq 0

Note that the minimun sample size, restricted to the predefined power \beta and confidence 1-\alpha, is defined by:

n = \frac{S^2}{\frac{D^2}{(z_{1-\alpha} + z_{\beta})^2}+\frac{S^2}{N}}

where S^2=(\sigma_1^2 + \sigma_2^2) * (1 - (T * R)) * DEFF

Author(s)

Hugo Andres Gutierrez Rojas <hagutierrezro at gmail.com>

References

Gutierrez, H. A. (2009), Estrategias de muestreo: Diseno de encuestas y estimacion de parametros. Editorial Universidad Santo Tomas

See Also

ss4pH

Examples

ss4dmH(N = 100000, mu1=50, mu2=55, sigma1 = 10, sigma2 = 12, D=3)
ss4dmH(N = 100000, mu1=50, mu2=55, sigma1 = 10, sigma2 = 12, D=1, plot=TRUE)
ss4dmH(N = 100000, mu1=50, mu2=55, sigma1 = 10, sigma2 = 12, D=0.5, DEFF = 2, plot=TRUE)
ss4dmH(N = 100000, mu1=50, mu2=55, sigma1 = 10, sigma2 = 12, D=0.5, DEFF = 2, conf = 0.99, 
       power = 0.9, plot=TRUE)

#############################
# Example with BigLucy data #
#############################
data(BigLucy)
attach(BigLucy)

N1 <- table(SPAM)[1]
N2 <- table(SPAM)[2]
N <- max(N1,N2)

BigLucy.yes <- subset(BigLucy, SPAM == 'yes')
BigLucy.no <- subset(BigLucy, SPAM == 'no')
mu1 <- mean(BigLucy.yes$Income)
mu2 <- mean(BigLucy.no$Income)
sigma1 <- sd(BigLucy.yes$Income)
sigma2 <- sd(BigLucy.no$Income)

# The minimum sample size for testing 
# H_0: mu_1 - mu_2 = 0   vs.   H_a: mu_1 - mu_2 = D = 3
D = 3
ss4dmH(N, mu1, mu2, sigma1, sigma2, D, DEFF = 2, plot=TRUE)

# The minimum sample size for testing 
# H_0: mu_1 - mu_2 = 0   vs.   H_a: mu_1 - mu_2 = D = 3
D = 3
ss4dmH(N, mu1, mu2, sigma1, sigma2, D, conf = 0.99, power = 0.9, DEFF = 3.45, plot=TRUE)