Analysis Of Variance Flashcards
What is ANOVA?
Analysis of variance
What is ANOVA used for?
To compare the mean of an interval scale variable between three or more independent groups
What is a one-way ANOVA?
The interval scale variable is compared between groups classified by just one variable
Why use ANOVA and not several independent samples t-tests?
i) using several tests would greatly increase the likelihood of a type l error
ii) Provided the assumptions hold, paired comparisons do use all the available data information about the variance of the interval scale variable of interest
How does two-way ANOVA work?
The interval scale variable is classified by two variables for simultaneous investigation
What are assumptions made when using one-way ANOVA?
If any of the sample sizes are less than 30….
i) The interval scale variable of interest should be normally distributed in the populations from which the samples came.
ii) The standard deviation in each of the populations should be similar
What are the components that variance are split into in order to use ANOVA?
Between group variation
Within group variation
Why might further tests be done following an ANOVA?
There is evidence of a difference in population means and further analysis can determine which groups differ
What are the two further tests that can be done after an ANOVA?
A priori hypotheses
A posteriori hypotheses
What is a priori hypotheses and how is it done?
Comparisons which the experiment was designed to test.
A straightforward comparison of two means may be conducted using a modified t-test
What are posteriori hypotheses and how are they done?
Comparisons which have been suggested by the data.
Correction do the data is necessary.
Tests of such hypotheses are referred to as post-hoc testing and should be treated with skepticism
