Final exam questions Flashcards
In a 2-way within-subjects ANOVA, there are n participants. ______
True.
In a 2-way mixed-factors ANOVA where A is the within-subjects factor, there are a n participants. ______
False
For a 2-way within-subjects ANOVA, the main effects of the treatments and the interaction are all tested using different MSError terms. ______
True
For a 2-way mixed-factors ANOVA, the main effects of the treatments and the interaction are all tested using different MSError terms. ______
False
The maximum value of eta^2 is ∞. ______
False
For treatment A in a 2-way design, the value of partial eta^2A is always greater than or equal to the value of eta^2A. ______
True
For a 1-way design, the value of eta^2 does not depend on whether you perform a within-subjects or between-subjects analysis. ______
True
A small Cohen’s effect size, f, for an ANOVA means that the null hypothesis will fail to be rejected. ______
False
9) ANOVA is robust to violations of homogeneity of variance so long as the design is balanced. ______
True
In a 1-way within-subjects analysis, if n = 8 then dfSubjects = 7. ______
True
In a 1-way within-subjects analysis, if N = 32 and you find F(3,21) = 3.12 then n = 11. ______
False
n^2 and r^2 are similar in that they both range between 0 and 1.
True
for a simple ANOVA, the df between is:
k-1
for a simple ANOVA, the df within is:
N-k
MS is…?
sums of squares of variance
Xji is such that j refers to
the order of group overall/level
Xji is such that i refers to
the order of the individual observation in a group
what is the structural model?
a method to decipher the individual sample as a part of an ANOVA, as it differs from the local treatment as well as the mean of all observations
what is the process by which all treatment means depart from a so-called grand mean?
centering
what are all treatment means departing from when compared to the mean of all observations?
the grand mean
once the data are centred, what can the structural model be viewed as accounting of?
why any observation deviates from the ground mean
what is the structural model for ANOVA composed of?
the total deviation of an observation from the grand mean which equals
the component of the deviation that is due to treatment differences, plus
the component of the deviation that cannot be accounted for by treatment differences
for the structural model, what does the total deviation from the mean look like between levels?
a bell curve on the left has its datapoint reaching as far to the centre mean/grand mean
for the structural model, what does the ERROR/within deviation from the mean look like between levels?
a bell curve on the left has its datapoint reaching to the centre of the LOCAL mean
for the structural model, what does the TREATMENT/between deviation from the mean look like between levels?
a bell curve on the left and the difference between that local mean from the grand mean
what are other names for treatment in the structural model?
the explained, or between
what are other names for error in the structural model?
the unemplained or within
What according to the structural model describes a treatment effect?
the between component (or “group” or “treatment” or “explained” component”) expresses the extent to which treatment j shifts the mean of its population from the overall mean
What would the structural model characterize as the “sums of squares”?
the sums and then squared of the individual deviations of observations in each sample in the dataset from the overall mean
What would the structural model characterize as the F-ratio?
the between variance from the mean over the within variance from the mean
What does ANOVA terminology call a variance?
“mean squares”
What are the degrees of freedom for dftotal for a 1-way anova?
dftotal = total numbers of observations minus 1, or N - 1
What are the degrees of freedom for dftbetween for a 1-way anova?
dfbetween = # of groups/levels/treatments minus 1, or k - 1
What are the degrees of freedom for dfwithin for a 1-way anova?
dfwithin = dftotal - dfbetween
What is the structural model for a 1-way ANOVA?
(Xji-u) = Tj + Eji
According to the structural model, what is the ANOVA ratio, or F?
the ratio of MS estimates of the variance in the population
What are the degrees of freedom for error in a 1-way ANOVA?
dferror = k(n-1); OR….dftotal - dftreatment
Do degrees of freedom depend on experimental results in a 1-way ANOVA?
No
What is the formula for MS in the ANOVA table?
Respective SS/respective df = same MS
What is a general term for ANOVA designs with more than 1 independent variable?
a multi-way ANOVA
Are treatments/factors determined randomly?
Not necessarily. Such can include gender, which is inherent to the participant and not malleable
What are the different categories of eacah treatment called?
levels
What is a key attribute of a design having multiple independent variables?
multiple treatments are applied simultaneously
How does a multiple anova differ in tabling data?
1-way = k = # of treatments 2-way = a for 1st level, b for 2nd level, etc. (axb)
if you have 2 levels of treatment a, and 3 levels of treatment b, what would you label individual datapoints?
xa,b,order in group
e.g. item 4 in level a2 b3 would be X234
What is each particular combination of treatment levels within the design for a multiple ANOVA design called?
a cell
Why do observations within a cell differ?
Solely due to experimental error
What is the cell mean?
The mean of all observations within a particular cell, similar to the treatment means for 1-way ANOVA design
What is the formula for number of observations in a multiple ANOVA design?
N = sum (nkj);
if 2-way, axbxn
What are designs where all the cells have observations?
a factorial design; if all the same, a balanced factorial design
How would you indicate a test for a ___ effect in a multiple ANOVA?
The simple effect of IV1 on DV, for IV2 level 2 (e.g. the simple effect of intervention on stress for/at females (from gender)
What kind of test can follow those for simple effects?
pairwise comparisons (or multiple pairwise comparison t-tests)
How would you plot a simple effect of B on A1 or A2?
You would likely plot an interaction plot with the levels of B on the horizontal axis, the interval amount for DV on the horizontal axis, and then 2 lines both indicating points for A1 and another for A2 to signify the simple effect of B on each of them at different levels of B
After you plot a simple effect, are you done?
No! a t-test needs to be determined in order to assess whether it is significant; at present it is simply a visual analysis
How many possible simple effects can be investigated using an a x b factorial ANOVA?
a + b possible simple effects
What do you typically consider main effect?
collapsing across levels of a variable in an effect; the effect of IV1 on DV (with no mention of IVx anywhere)
What do you calculate when you collapse across means in the margins of a 2-way table in order to calculate the means necessary for examining the main effect of one fof the IVs?
the marginal means
Is it possible to have a main effect for one IV but not the other?
yes
What is the best order to assess effects?
interaction, simple and then (if applicable), main
What is another way of indicating an interaction?
a modulation of the simple effects of IV2 by the variable IV1
What are 2 points about interaction effects?
1 - the lines in an interaction plot DO NOT need to cross for an interaction to be present
2 - the lines in an interaction plot may be nonparalleld due only to sampling variability, i.e., there is no real interaction only an apparent one due to sampling variability
Is it possible for an interaction to be present even if neither variable exhibits a main effect?
Yes. It can simply be interactions masking main effects
Analyses in which there is only 1 DV are called “” analyses
“univariate”
What is the structural model formula for a 2-way ANOVA?
Xkji - u = ak + Bj + aBkj+Ekji , or Xkji - u = Tkj + Ekji; ak = effect of treatment a; Bj = effect of treatment B; aBkj = effect of a x b interaction
What do the terms in the structural model form?
the various sum-of-squares used in a 2-way ANOVA; Xkji - u = SStotal; ak = SSa; Bj = SSB; aBkj = SSaxb; Ekji = SSerror
For the Eysenck example of age x instruction on time(?), what would be on the ANOVA table?
Source would have: age/a instruction/b age x instruction/axb error/E total
What are the degrees of freedom for ak or Bj (main effects) in the ANOVA table?
k - 1
What is the df for an interaction in the ANOVA table?
product of all df for main effects: dfa x dfb (NOT ka x kb)
What is used to form all F-ratios in a 2-way ANOVA?
the MSerror, which estimates the within estimate of population variance
What do each of the F-ratios in a 2-way ANOVA test?
either a main effect or an interaction effect
what is the structural model of overall effect?
Xkji - u = Tkj + Ekji; you would calculate the SSexplained by adding all of the SSmain and interaction effects together, , or you can take the SStotal and substract the SSerror to get the explained total. You can also for df take the dftotal and subtract the dferror to get the dfexplained…you are ignoring the a, b, and axb levels in favour of aggregating them…and the MSexplained can be done by SSexplained/dfexplained= MSexplained
What is the explained model entry called in SPSS?
the “corrected model” entry
what are two measurements of effect size for ANOVA?
Cohen’s f, and n^2 (similar to r^2, a popular regression technique)
What are the properties for effect sizes in ANOVA?
- hey don’t depend on measurement scales
- they don’t depend on sample size
- they don’t depend on arbitrary choices made to increase statistical power (e.g. creating a larger alpha)
- they are useful in meta-analysis
What does n^2 refer to?
magnitude of the effect, or proportion of explained variation in dependent variable values that is associated with differences in the independent variable
How is n^2 pronounced?
eta squared
What is the 1-way ANOVA magnitude of the effect formula?
n^2 = SStreatment/SStotal
What does the value of n^2 always lie between?
0 and 1 (it’s a proportion, therefore a fraction of a total, i.e. 1)
What is eta squared according to the null hypothesis?
n^2 = 0
What also does the magnitude of the effect measure?
the importance of the effect (e.g. an effect may be significant, but is it important?)
Again, what is the formula for magnitude of the effect for 1-way ANOVA?
SStreatment (or SS explained) / SStotal
what does SPSS call leta squared or n^2?
R squared, since it works like the r^2 in regression problems
What is another way of indicating that the ANOVA tests the null hypothesis such that n^2 = 0?
the null hypothesis consists of saying that differences in treatment do not explain any of the variation in the dependent variable
Is eta squared a biased or unbiased estimator of the true proportion of variance?
biased
Why is eta squared a biased estimator of the true proportion of variance?
it overshoots the mark when attempting to explain how treatments affect a population
What is an unbiased estimator for the proportion of explained variation in the population?
quantity, or “adjusted R squared”; the formula for 1-way anova is =
sStreatment = (k1) MSerror/
(SStotal + MSerror)
How do you calculate eta squared for 2-way ANOVA?
SEPARATE N^2 FOR EACH FACTOR/VARIABLE (a, b, and axb):
Na^2 = SSa/SStotal
Nb^2 = SSb/SStotal
Naxb^2 = SSaxb/SStotal
What is the value for each eta squared calculation for each variable of a two-way anova?
Each one befit a proportion, therefore each one has a value that is between 0 and 1