Summa Week 10 Flashcards
2 and 3
What is factorial ANOVA between-subjects design?
2 or more IV each with multiple levels
In Factorial ANOVA, are the levels of IV fixed or continuous?
fixed
In Factorial ANOVA, are participants randomly or purposely assigned to levels, and if so, how many?
randomly assigned
assigned to only ONE combo of the levels
In Factorial ANOVA, are levels of one variable possible for all levels of other variables?
Yes. This is called being “fully crossed”
In Factorial ANOVA, how are DVs measured?
continuously
In Factorial ANOVA, what is the SS formula?
SStotal = SSa + SSb + SSab + SSerror
In Factorial ANOVA, what is SStreatment (change due to the model)?
SSa (main effect of a) + SSb (main effect of b) + SSab (interaction effect)
In Factorial ANOVA, what is added to SStreatment to equal the SStotal, or total variance in the data?
SSerror (error in the model)
What is a main effect?
the effect of one IV averaged over the other variable or when the other variable is ignored
e.g. Assignment 4, Study 2
main effect of reinforcement scheduling on studying practices
What is an interaction effect?
one IV is modified by the levels of another variable
e.g. Assignment 4, Study 2
interaction effect of reinforcement schedule on levels of reinforcer type
What is a simple effect?
the effect of one variable at a SPECIFIC level of another IV
e.g. Assignment 4, Study 2
simple effect of random scheduling on studying
What is the ANOVA summary table for 2-way analysis?
Source SS df MS F
A SSa a-1 MSa MSa/MSerror = main effect A
B SSb b-1 MSb MSb/MSerror = main effect B
AxB SSab (a-1)(b-1) MSab MSab/MSerror = interactino
Within SSerror ab(n-1) MSerror
Total SStotal N-1
What is the same calculation for two-way ANOVA and one-way?
Total = SStotal, and df = N-1
When should the main effects be further examined?
only when there is NOT a significant interaction effect. The presence of a significant interaction LIMITS the sense of the main effects - it is difficult to make a general statement about a variable’s effect when the size of the effect depends on the level of a second variable
A significant interaction indicates what?
that the effect of ONE IV differs depending on the LEVEL of another IV
Why are main effects misleading in the presence of interaction terms?
taking the crossing line plot for yield by temperature and pressure, although the lines intersect, there is no main effect of pressure because the average score at the two pressures is the same. So note that it doesn’t mean that pressure has no effect on the yield but that there is when it interacts with temperature
When two lines in a factorial anova line chart are parallel, this indicates:
no significant interaction
When two lines in a factorial anova touch or cross, this indicates:
a significant interaction
What do you do after noting a significant interaction effect?
test the simple effects!
What does testing the simple effects of an interaction effect require?
NO follow-up tests; examination of the interaction plot
Why aren’t supplemental analyses required if the researcher sees an interaction effect?
the data also can provide information on how one variable differs depending on the level of another variable, which indicates a simple effect, the goal of further analysis
What is the factorial anova formula for SStotal?
SStotal = Sum of (Xijn - X_..)^2
Sums of squares total equals the sum of data points each subtracted by the grand mean, squared
What is the factorial anova formula for SStask?
SStask = nc x sum of (data from column/task of inquity - X_..)^2
sums of squares for task equals the number of comparisons x sum of data points for the task each subtracted by the grand mean, squared
What is the factorial anova formula for SScondition?
SScondition = na x sum of (data points for the condition - X_..)^2
sums of squares for condition equals the number of conditions for variable A x sum of data points for the condition each subtracted by the grand mean, squared
What is the factorial anova formula for SScell?
SScell = n x sum of (data points for the individual cell - X_..)^2
sums of squares for cell equals the number of cells x sum of data points for the cell each subtracted by the grand mean, squared
What is the factorial anova formula for SStc?
SStc = SScell - SStask - SScondition
What is the factorial anova formula for SSerror?
SSerror = SStotal - SScell
How can you tell in a table if there are very large differences in means in the different tasks but small differences among conditions?
Decide using this data for analysis:
Smoking Pattern Recall Driving Total
Condition Task Simulation
Nothing 9.40 28.87 9.93 16.07
delayed 9.60 39.93 6.80 18.78
active 9.93 47.53 2.33 19.93
total 9.64 38.78 6.36 18.26
the differences under each task (pattern, recall, driving) all differ quite a lot, but the totals for conditions do not vary that much
Using this data for analysis, what can we say about the task and smoking condition?
Smoking Pattern Recall Driving Total
Condition Task Simulation
Nothing 9.40 28.87 9.93 16.07
delayed 9.60 39.93 6.80 18.78
active 9.93 47.53 2.33 19.93
total 9.64 38.78 6.36 18.26
it looks as if there is a difference due to task and to smoking condition, which are main effects because they are the effect of one variable AVERAGED over the other variables