Spower (version 0.6)

p_wilcox.test: p-value from Wilcoxon (signed rank) test simulation

Description

Simulates data given one (Wilcoxon) or two (Mann-Whitney) parent distributions and returns a p-value. Can also be used for power analyses related to sign tests.

Usage

p_wilcox.test(
  n,
  d,
  n2_n1 = 1,
  mu = 0,
  type = c("two.sample", "one.sample", "paired"),
  exact = NULL,
  correct = TRUE,
  two.tailed = TRUE,
  parent1 = function(n, d) rnorm(n, d, 1),
  parent2 = function(n, d) rnorm(n, 0, 1),
  return_analysis = FALSE
)

Value

a single p-value

Arguments

n

sample size per group. For paired samples this corresponds to the number of pairings (hence, half of the data points observed)

d

effect size passed to parent functions

n2_n1

sample size ratio

mu

parameter used to form the null hypothesis

type

type of analysis to use (two-sample, one-sample, or paired)

exact

a logical indicating whether an exact p-value should be computed

correct

a logical indicating whether to apply continuity correction in the normal approximation for the p-value

two.tailed

logical; use two-tailed test?

parent1

data generation function for first group. Ideally should have SDs = 1 so that d reflects a standardized difference

parent2

same as parent1, but for the second group

return_analysis

logical; return the analysis object for further extraction and customization?

Author

Phil Chalmers

Examples

# with normal distributions defaults d is standardized
p_wilcox.test(100, .5)
p_wilcox.test(100, .5, type = 'paired')  # n = number of pairs
p_wilcox.test(100, .5, type = 'one.sample')

# return analysis object
p_wilcox.test(100, .5, return_analysis = TRUE)

# using chi-squared distributions (standardizing to 0-1)
p_wilcox.test(100, .5, type = 'one.sample',
   parent1 = function(n, d) rchisq(n, df=10) - 10 + d)
p_wilcox.test(100, .5,
   parent1 = function(n, d) (rchisq(n, df=10) - 10)/sqrt(20) + d,
   parent2 = function(n, d) (rchisq(n, df=10) - 10)/sqrt(20))