week 4 - one-way between subject ANOVA Flashcards
What is the purpose of correlation?
to find out if there is an association between two continuous variables.
What is the purpose of simple regression?
to find out the extent of the linear relationship between the outcome variable and the predictor variable.
Which test should you run for the following research question; are Gryffindor players better than Slytherin players?
between-subject t-test
Which test should you run for the following research question; Is exam scores on Defence Against the Dark Arts associated with performance in Quidditch (game score)?
within-subject t-test
Which test should you run for the following research question; Ron Weasley wanted to estimate and predict his Defence Against the Dark Arts exam score based on his Quidditch performance. What test should he run?
one way between-subject ANOVA
Which test should you run for the following research question; Are Gryffindor players the best compared to the other 3 houses?
one way within-subject ANOVA
What is ANOVA?
ANalysis Of VAriance. A statistical test for three or more groups or conditions (or a combination of groups and conditions).
What are the two types of ANOVA?
Between-subject/Independent samples ANOVA and within-subject/related-samples ANOVA?
When is between-subject/independent sample ANOVA used?
When there are three or more groups.
When is within-subject/related-sampled ANOVA used?
When there are three or more conditions.
ANOVA with both between-subject and within-subject factors is called…
A multi-factorial or mixed ANOVA.
Explain groups and levels in; Are Gryffindor players the best compared to the other 3 houses?
groups: 4 levels: Gryffindor, Slytherin, Ravenclaw, Hufflepuff
Explain conditions and levels in; Harry wanted to know if whoever uses Thunderbolt are better than when they use Firebolt or Nimbus 2000.
conditions: 3 levels: thunderbolt, firebolt, nimbus 2000
What are F-tests?
Used by ANOVA to statistically test if the means are different across groups or conditions.
What does F-test produce?
An F-ratio to inform us if the variability between group means is larger than the variability of the observations within the groups (i.e., error).
ANOVA is an omnibus test, what does that mean?
it tests for an overall experimental effect. (i.e. we don’t know which groups or conditions differed.)
Why not do multiple t-tests?
Increases chance of type 1 error.
what is the family-wise error rate?
the greater the number of tests, the greater the chance of type 1 error.
What does the F-ratio compare?
amount of systemic variance(variance due to what we know) to unsystematic variance(variance due to what we don’t know).
What are the three types of variation (sum of squares)?
total sum of squares, model sum of squares, and residual sum of squares.
What are post-hoc tests needed for?
with omnibus test we don’t know which groups are different specifically.
What is the Tukey HSD test designed for?
So you can compare as many things as you want without inflating the family-wise error rate.
How do you report Tukey HSD test results?
It produces no test statistic, only a p-value so we describe the finding in the text.
What is cohen’s D for post-hoc testing?
difference between means divided by standard deviation.
To calculate F in a one-way independent ANOVA, the variance between groups is divided by the variance within groups. To calculate the variance between groups you need to work out the residual sum of squares. To do this:
You take each individual score, subtract the mean for the group it belongs to, square the answer, and add all of these values together.
