WRS2 (version 0.3-1)

t2way: A two-way ANOVA for trimmed means, M-estimators, and medians.

Description

The t2way function computes a two-way ANOVA for trimmed means with interactions effects. Corresponding post hoc tests are mcp2atm. pbad2way performs a two-way ANOVA using M-estimators for location with mcp2a for post hoc tests.

Usage

t2way(formula, data, tr = 0.2)
pbad2way(formula, data, est = "mom", nboot = 599)
mcp2atm(formula, data, tr = 0.2)
mcp2a(formula, data, est = "mom", nboot = 599)

Arguments

formula

an object of class formula.

data

an optional data frame for the input data.

tr

trim level for the mean.

est

Estimate to be used for the group comparisons: either "onestep" for one-step M-estimator of location using Huber's Psi, "mom" for the modified one-step (MOM) estimator of location based on Huber's Psi, or "median".

nboot

number of bootstrap samples.

Value

• The functions t2way and pbad2way return an object of class t2way containing:
• Qa
  first main effect
• A.p.value
  p-value first main effect
• Qb
  second main effect
• B.p.value
  p-value second main effect
• Qab
  interaction effect
• AB.p.value
  p-value interaction effect
• call
  function call
• varnames
  variable names
• The functions mcp2atm and mcp2a return an object of class mcp containing:
• effects
  list with post hoc comparisons for all effects
• contrasts
  design matrix

Details

pbad2way returns p-values only.

References

Wilcox, R. (2012). Introduction to Robust Estimation and Hypothesis Testing (3rd ed.). Elsevier.

See Also

t1way, med1way

Examples

## 2-way ANOVA on trimmed means
t2way(attractiveness ~ gender*alcohol, data = goggles)

## post hoc tests
mcp2atm(attractiveness ~ gender*alcohol, data = goggles)

## 2-way ANOVA on MOM estimator
pbad2way(attractiveness ~ gender*alcohol, data = goggles)

## post hoc tests
mcp2a(attractiveness ~ gender*alcohol, data = goggles)

## 2-way ANOVA on medians
pbad2way(attractiveness ~ gender*alcohol, data = goggles, est = "median")

## post hoc tests
mcp2a(attractiveness ~ gender*alcohol, data = goggles, est = "median")

## extract design matrix
model.matrix(mcp2a(attractiveness ~ gender*alcohol, data = goggles, est = "median"))