jmv (version 2.4.11)

ttestOneS: One Sample T-Test

Description

The Student's One-sample t-test is used to test the null hypothesis that the true mean is equal to a particular value (typically zero). A low p-value suggests that the null hypothesis is not true, and therefore the true mean must be different from the test value.

Usage

ttestOneS(data, vars, students = TRUE, bf = FALSE, bfPrior = 0.707,
  wilcoxon = FALSE, testValue = 0, hypothesis = "dt", norm = FALSE,
  qq = FALSE, meanDiff = FALSE, ci = FALSE, ciWidth = 95,
  effectSize = FALSE, ciES = FALSE, ciWidthES = 95, desc = FALSE,
  plots = FALSE, miss = "perAnalysis", mann = FALSE)

Value

A results object containing:

results$ttest					a table containing the t-test results
results$normality					a table containing the normality test results
results$descriptives					a table containing the descriptives
results$plots					an image of the descriptive plots
results$qq					an array of Q-Q plots

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

results$ttest$asDF

as.data.frame(results$ttest)

Arguments

data

the data as a data frame

vars

a vector of strings naming the variables of interest in data

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 2.0 (default 0.707), the prior width to use in calculating Bayes factors

wilcoxon

TRUE or FALSE (default), perform Wilcoxon signed rank tests

testValue

a number specifying the value of the null hypothesis

hypothesis

'dt' (default), 'gt' or 'lt', the alternative hypothesis; different to testValue, greater than testValue, and less than testValue respectively

norm

TRUE or FALSE (default), perform Shapiro-wilk tests of normality

qq

TRUE or FALSE (default), provide a Q-Q plot of residuals

meanDiff

TRUE or FALSE (default), provide means and standard deviations

ci

TRUE or FALSE (default), provide confidence intervals for the mean difference

ciWidth

a number between 50 and 99.9 (default: 95), the width of confidence intervals

effectSize

TRUE or FALSE (default), provide Cohen's d effect sizes

ciES

TRUE or FALSE (default), provide confidence intervals for the effect-sizes

ciWidthES

a number between 50 and 99.9 (default: 95), the width of confidence intervals for the effect sizes

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.

mann

deprecated

Details

The Student's One-sample t-test assumes that the data are from a normal distribution -- in the case that one is unwilling to assume this, the non-parametric Wilcoxon signed-rank can be used in it's place (However, note that the Wilcoxon signed-rank has a slightly different null hypothesis; that the *median* is equal to the test value).

Examples

data('ToothGrowth')

ttestOneS(ToothGrowth, vars = vars(len, dose))

#
#  ONE SAMPLE T-TEST
#
#  One Sample T-Test
#  ------------------------------------------------------
#                           statistic    df      p
#  ------------------------------------------------------
#    len     Student's t         19.1    59.0    < .001
#    dose    Student's t         14.4    59.0    < .001
#  ------------------------------------------------------
#