Chapter 12: Experiments with More than One Independent Variable

Independent-groups factorial (there are 4 groups in the experiment: large weekly consumers who see the alc commercials, large weekly consumers who see non alc, small weekly consumers who see alc, small weekly consumers who see nonalcoholic commercials)

A recent studied conducted in the Netherlands on the effect of commercial s for alc or no alc consumption in the movie theatre found that young adults who consume large amounts of alc each week are influenced by the commercials, whereas young adults who consume small amounts of alc each week are not influenced. Participants saw one of two types of beverage commercials: alcoholic or nonalcoholic. Their consumption during the movie was measured. What type of design was this?

Main effect of role, no effects of other present and an interaction

Describe her results: the values in the first row are 10,20 and 20. The second row the values are 20,10 and 10.

external validity

Factorial design enhances ______ _________ (by testing effect of IV under multiple conditions)

generalizability

Factorial designs can check the _____________ of a causal variable and find if variable interactions are consistent with those predicted by theories

6 (3x2:The number of levels multiplied is the number of conditions)

For a specific design (e.g., 3 x 2) How many conditions?

6

For a specific design (e.g., 3 x 2) How many interactions are tested?

3 levels of the first factor and 2 levels of the second facter

For a specific design (e.g., 3 x 2) How many levels of each?

2 because there are 2 independent variables

For a specific design (e.g., 3 x 2) How many main effects are tested?

2 factors

For a specific design (e.g., 3 x 2) o How many IVs/Factors?

Amount of alc consumed by the young adults during the week (the weekly alc consumption of the participant was selected, not manipulated)

Found that young adults who consume large amounts of alc each week are influenced by the commercials, whereas young adults who consume small amounts of alc each week are not influenced. What is a participant variable in this study?

6 (the study was run within-groups, each golfer was in each cell)

Gucciardi and Dimmock reported on an experiment on choking under pressure in skilled golfers. They varied anxiety level and putting condition in a 2x3 within groups design. Anxiety level (low or high) was varied with a competition with financial compensation being introduced following the low anxiety-level performance. Mean distance from hole was computed for the 10 putts in each condition. How many cells were each golfer in?

2 main effects and one interaction (there are 2 independent variables, so there are 2 main effects and 1 interaction possible even though 1 variable has 3 levels)

Gucciardi and Dimmock reported on experiment on choking under pressure in skilled golfers. They varied anxiety level and putting condition in a 2x3 within-groups design. Anxiety level (low/high) was varied with a competition being introduced following the low-anxiety trials. The putting conditions were thinking of cue words about either putting technique, irrelevant items or a single thought such as "smooth". Mea distance was computed from the 10 putts in each condition. What are all the differences that must be examined?

main effects, interaction effect

How do you interpret main effects and interactions? In a factorial design with 2 independent variables, the first 2 results obtained are the _____ _______ for each independent variable. The 3rd result is the ______ _____________.

3, 24

How many independent variables and how many cells are there in a 2x2x4 study? ____ independent variables, _____ cells

depends

Three-way interactions (2x2x2 design) o If it is significant, means that the 2-way interaction between 2 of the independent variable ____________ on the level of the 3rd variable o In a three-way design, the final result is a single three-way interaction.

60 (adding the third between groups factors make 60 necessary—20 for each level)

To achieve a goal of 20 observations per cell in a 2x2x3 mixed experiment with the 1st 2 factors run within groups and the last factor run between groups, what would be the # of participants needed?

main effects, interactions, interaction (each factor must be checked for a main effect, each of the possible two-way interactions must be checked and the three-way interaction must be checked)

What differences need to be investigated when a 3-way design is used? Three ___________, three two-way __________ and a three-way ____________

Interaction (means there is a difference in differences)

What is it called when the effect of one independent variable depends on the level of the other independent variable?

3

When a factorial design has 3 independent variables in a 2x2x2 design, there will be __ main effects to test.

important

When a study shows an interaction itself is the most _______ effect

Correlation

When authors of a research article are describing just the result of a factorial study, which of these terms would you not expect to see?

Factorial design:

When there are 2 or more independent variables

ANOVA

-will give you a p value for the main effect of each factor separately -will give you a p value for interactions between factors

limits, theories

2 reasons to use factorial designs To test ________ and to test ________

2, 1

2x2 factorial design: ____ levels of _____ independent variable are crossed with 2 levels of another independent variable

4

2x2, _____ cells in this design

Type of commercial shown (independent variables are also called factors)

A recent studied conducted in the Netherlands on the effect of commercials for alc or no alc consumption in the movie theatre found that young adults who consume small amounts of alc each week are influenced by the commercials, whereas young adults who consume small amounts of alc each week are not influenced. Participants saw one of two types of beverage commercials: alcoholic or nonalcoholic. Their consumption of alcohol during the movie was measured. What is a factor in this study?

Main effect:

A simple difference or overall effect

No effect, main, interaction

After reading a report by Rockoff, Ying is studying the effect of others present and their roles on the gambling bets using a stimulated slot machine. Her levels of others present are 1, 2, or 6. Her levels of roles are gamblers and observers. She constructs a 2x3 table of her results of average time between bets. There are 2 rows for the roles and 3 columns for the other present. The values in the first rows are 15, 15,15. In the 2nd row are 20, 15 and 10. Describe her results ___ _____ of role, ______ effect of others present and _________

2-way interaction between price and consumer (this means that in looking at the tastiness and expensiveness of ratings for self, there is a smaller difference between the inexpensive and expensive ratings that there is in those ratings for classmate)

An and Sen gupta examined the effects of price, attractiveness and consumer on the perceived tastiness and expensiveness of fried rice. The study was a 2x2x2 design that varied price (inexpensive or expensive, picture) (attractive or not), and consumer (self or classmate) in between-subjects design. A main effect of price and a main effect of picture were found. It was found that the impact of price on tastiness/expensiveness judgments was weaker in the self than in the classmate. What type of interaction does this describe?

difference in differences

An interaction is a ____ ____ ____, so you start by computing 2 differences

It depends

An interaction is present when the answer to a question about the effect of an IV is "___ _____"

Independent-groups factorial design:

If the design is a 2x2, there are 4 different groups or participants in the experiment − If the researchers decided to use 50 participants in each cell, they'd need 200 participants o 50 in each of the four groups

Within-groups factorial design:

If the design is a 2x2, there is only one group of participants, but they participate in all 4 combinations of the design.

non-parallel

If the lines _________, there is probably an interaction

parallel

If the lines are _______, there is probably no interaction

Mixed factorial design:

In a 2x2, you have 4 different groups of participants, each only experiencing 1 condition, and the other is manipulated as within groups (1 group of participants, each participating in all combinations/cells of the design)

2

In a factorial design with 2 IV, there are ______ main effects

interaction (main effect=overall effect)

In a factorial design, which is the most important effect?

200 (50 in each of the four groups)

Independent-groups factorial design: If the researchers decided to use 50 participants in 4 groupsl, they'd need ______ participants

marginal means

Main effects may or may not be statistically significant Researchers look at _____ ___________ to inspect the main effects in a factorial design and they use statistics to find out whether the difference in the marginal means is statistically significant

Mixed factorial design:

One independent variable is manipulated as independent groups and the other is manipulated as within-groups.

Participant variable:

One that the experimenter does not actually manipulate, but is selected (example: age, sex, education)

Interaction:

The effect of one IV changed based on the level of another IV

Main effect:

The overall effect of one independent variable on the dependent variable, averaging over the levels of the other independent variable

2-way interaction between picture and consumer (there is a larger difference between the attractive and unattractive ratings than those in those ratings for classmate)

The study of a 2x2x2 design that varied price (expensive or inexpensive), picture (attractive or unattractive) and consumer (self or classmate) in a between subject's design. A main effect of price and a main effect of picture were found. It was found that the picture had a greater impact on tastiness/expensiveness judgments in self than in classmate. What type of interaction does this describe?

No effect of role, no effect of others present, and an interaction (marginal means are the same for both factors and there are differences in the differences in the column)

The values in the first row are 10,15, 20 and in the second row are 20,15, 10. Describe her results

simple, difference in differences

Whereas the main effects are _____ differences, the interaction effect is the _______________

50 (each participant would participate in each of the 4 possible combinations)

Within-groups factorial design: If there were 50 participants, you would need a total of _______ participants

Marginal means

______ _________ are used to inspect the main effects and in the case of a not significant main effect of anxiety, they are very close to each other. (_____ _______ for the 2 anxiety conditions are not significantly different)

independent variable

what is a factor also called?

factorial design

what type of design would be a cue when they use the phrases "it depends", use of participant variable as well as other independent variables, phrasing that suggests that there was a difference in differences