d.ind.t.t: d from t for Between Subjects

In doomlab/MOTE: Effect Size and Confidence Interval Calculator

d from t for Between Subjects

Description

This function displays d for between subjects data and the non-central confidence interval estimating from the t-statistic.

Usage

d.ind.t.t(t, n1, n2, a = 0.05)

Arguments

t	t-test value
n1	sample size group one
n2	sample size group two
a	significance level

Details

To calculate d, the t-statistic is multiplied by two then divided by the square root of the degrees of freedom.

d_s = 2 * t / sqrt(n1 + n2 - 2)

Learn more on our example page.

Value

Provides the effect size (Cohen's d) with associated confidence intervals, degrees of freedom, t-statistic, and p-value.

d	effect size
dlow	lower level confidence interval of d value
dhigh	upper level confidence interval of d value
n1	sample size
n2	sample size
df	degrees of freedom (n1 - 1 + n2 - 1)
t	t-statistic
p	p-value
estimate	the d statistic and confidence interval in APA style for markdown printing
statistic	the t-statistic in APA for the t-test

Examples

#The following example is derived from the "indt_data" dataset, included
#in the MOTE library.

#A forensic psychologist conducted a study to examine whether
#being hypnotized during recall affects how well a witness
#can remember facts about an event. Eight participants
#watched a short film of a mock robbery, after which
#each participant was questioned about what he or she had
#seen. The four participants in the experimental group
#were questioned while they were hypnotized. The four
#participants in the control group recieved the same
#questioning without hypnosis.

    hyp = t.test(correctq ~ group, data = indt_data)

#You can type in the numbers directly, or refer to the dataset,
#as shown below.

    d.ind.t.t(t = -2.6599, n1 = 4, n2 = 4, a = .05)

    d.ind.t.t(-2.6599, 4, 4, .05)

    d.ind.t.t(hyp$statistic,
              length(indt_data$group[indt_data$group == 1]),
              length(indt_data$group[indt_data$group == 2]),
              .05)

#Contrary to the hypothesized result, the group that underwent hypnosis were
#significantly less accurate while reporting facts than the control group
#with a large effect size, t(6) = -2.66, p = .038, d_s = 2.17.

doomlab/MOTE documentation built on April 17, 2022, 2:08 a.m.