1-One-Mean: One Mean against a Constant (z or t Test)

In pwrss: Statistical Power and Sample Size Calculation Tools

One Mean against a Constant (z or t Test)

Description

Calculates statistical power or minimum required sample size (only one can be NULL at a time) to test a mean against a constant.

Formulas are validated using http://powerandsamplesize.com/, and tables in PASS documentation.

Usage

pwrss.t.mean(mu, sd = 1, mu0 = 0, margin = 0, alpha = 0.05,
             alternative = c("not equal","greater","less",
                             "equivalent","non-inferior","superior"),
             n = NULL, power = NULL, verbose = TRUE)

pwrss.z.mean(mu, sd = 1, mu0 = 0, margin = 0, alpha = 0.05,
             alternative = c("not equal","greater","less",
                             "equivalent","non-inferior","superior"),
             n = NULL, power = NULL, verbose = TRUE)

Arguments

mu	expected mean
sd	expected standard devation
mu0	constant to be compared (a mean)
n	sample size
power	statistical power (1-\beta)
alpha	probability of type I error
margin	non-inferority, superiority, or equivalence margin (margin: boundry of mu - mu0 that is practically insignificant)
alternative	direction or type of the hypothesis test: "not equal", "greater", "less", "equivalent", "non-inferior", or "superior"
verbose	if FALSE no output is printed on the console

Value

parms	list of parameters used in calculation
test	type of the statistical test (z or t test)
ncp	non-centrality parameter
df	degrees of freedom
power	statistical power (1-\beta)
n	sample size

References

Bulus, M., & Polat, C. (in press). pwrss R paketi ile istatistiksel guc analizi [Statistical power analysis with pwrss R package]. Ahi Evran Universitesi Kirsehir Egitim Fakultesi Dergisi. https://osf.io/ua5fc/download/

Examples

# Example: A researcher is expecting a score of 23
# on Beck depression inventory (BDI) which is
# 0.50 standard devation above the threshold value 20
# (assume standard deviation of BDI scores is 6).

# to find that a score of 23 is greater than the threshold 20
pwrss.t.mean(mu = 23, mu0 = 20, sd = 6,
             alpha = 0.05, power = 0.80,
             alternative = "greater")
# standardized formulation
pwrss.t.mean(mu = 0.50, mu0 = 0, sd = 1,
             alpha = 0.05, power = 0.80,
             alternative = "greater")

pwrss documentation built on April 12, 2023, 12:34 p.m.