testing for difference between 2 sample means Flashcards
finding a difference between our data conditions depends upon?
means
standard deviations/ variances
sample
descriptive statistics
means
medians
sds
confidence intervals
how do you messure ‘effect size’?
using cohens d
what is cohen’d D
a measure of distance between two condition means which takes variability (sds) into account
cohen’s d for population
d = u1-u2/ (o1+o2/2)
cohens d for sample
m1-m2/ (s1+s2/2)
0.2 cohens d indicates?
small effects size
85% overlap
0.5 cohens d indicates?
medium effect size
67% overlap
0.8 cohens d indicates?
large effect size
53% overlap
three hypothesis for testing differences between 2 sample means?
mean A is smaller than mean B
mean A is larger than mean B
mean A is not equal to mean B
null hypothesis for testing difference between 2 sample means?
mean A is equal to mean B
if probability calculated is sufficiently small?
we reject the null hypothesis in favour of the research hypothesis
what happens if we do not obtain a sufficiently small probability?
we fail to reject the null hypothesis
what tests can be used to compare differences between 2 sample means?
related t test
independent t test
when do you use the independent t test
when participants perform in only one of the conditions
