R: Independent Samples T-Test

ttestIS {jmv}

R Documentation

Independent Samples T-Test

Description

Independent Samples T-Test

Usage

ttestIS(data, vars, group, students = TRUE, bf = FALSE, bfPrior = 0.707,
  welchs = FALSE, mann = FALSE, hypothesis = "different", norm = FALSE,
  qq = FALSE, eqv = FALSE, meanDiff = FALSE, effectSize = FALSE,
  ci = FALSE, ciWidth = 95, desc = FALSE, plots = FALSE,
  miss = "perAnalysis")

Arguments

`data`	the data as a data frame
`vars`	a vector of strings naming the dependent variables
`group`	a string naming the grouping variable, must have 2 levels
`students`	`TRUE` (default) or `FALSE`, perform Student's t-tests
`bf`	`TRUE` or `FALSE` (default), provide Bayes factors
`bfPrior`	a number between 0.5 and 2 (default 0.707), the prior width to use in calculating Bayes factors
`welchs`	`TRUE` or `FALSE` (default), perform Welch's t-tests
`mann`	`TRUE` or `FALSE` (default), perform Mann-Whitney U tests
`hypothesis`	`'different'` (default), `'oneGreater'` or `'twoGreater'`, the alternative hypothesis; group 1 different to group 2, group 1 greater than group 2, and group 2 greater than group 1 respectively
`norm`	`TRUE` or `FALSE` (default), perform Shapiro-Wilk test of normality
`qq`	`TRUE` or `FALSE` (default), provide a Q-Q plot of residuals
`eqv`	`TRUE` or `FALSE` (default), perform Levene's test for equality of variances
`meanDiff`	`TRUE` or `FALSE` (default), provide means and standard errors
`effectSize`	`TRUE` or `FALSE` (default), provide effect sizes
`ci`	`TRUE` or `FALSE` (default), provide confidence intervals
`ciWidth`	a number between 50 and 99.9 (default: 95), the width of confidence intervals
`desc`	`TRUE` or `FALSE` (default), provide descriptive statistics
`plots`	`TRUE` or `FALSE` (default), provide descriptive plots
`miss`	`'perAnalysis'` or `'listwise'`, how to handle missing values; `'perAnalysis'` excludes missing values for individual dependent variables, `'listwise'` excludes a row from all analyses if one of its entries is missing.

Value

A results object containing:

`results$ttest`					a table containing the t-test results
`results$assum$norm`					a table containing the normality tests
`results$assum$eqv`					a table containing the equality of variances tests
`results$desc`					a table containing the group descriptives
`results$plots`					an array of groups of plots

Tables can be converted to data frames with asDF or as.data.frame. For example:

results$ttest$asDF

as.data.frame(results$ttest)

Examples

data('ToothGrowth')

ttestIS(data = ToothGrowth, vars = 'len', group = 'supp')

#
#  INDEPENDENT SAMPLES T-TEST
#
#  Independent Samples T-Test
#  ----------------------------------------------------
#                          statistic    df      p
#  ----------------------------------------------------
#    len    Student's t         1.92    58.0    0.060
#  ----------------------------------------------------
#

[Package jmv version 0.9.2.0 Index]