factorial designs: a visual approach

Factorial Designs: A Visual Approach

No numbers!

Research design explained

• This tutorial is based on the example study described on page 467 of Research designed explained.

• This tutorial is based on the example study described on page 420 of Research designed explained.

• In that study, all participants read 60 statements aloud. These statements were presented as a Powerpoint slide show.

• This tutorial is based on the example study described on page 420 of your text.


• However, not all slide shows were the same.

• This tutorial is based on the example study described on page 420.


• However, not all slide shows were the same. • Some slide shows presented negative statements

(e.g., “I feel a little low today”), whereas other slide shows presented positive statements (e.g., “I feel pretty good today”). Thus, some participants read positive statements, whereas others read negative statements.

• This tutorial is based on the example study described on page 420.


• However, not all participants read the same 60 statements. Some read positive statements (e.g., “I feel pretty good today, though”), whereas others read negative statements (e.g., “However, I feel a little low today”).

• In addition, the slide shows varied in how fast they presented the statements. Some slide shows presented the statements at a fast rate; others presented the statements at a slow rate. Thus, some participants had to read and say the statements at a fast pace; the other participants did so at a slow pace.

Visually, we can diagram the design as follows:

Participants

Negative statements Positive statements

Slow SlowFast Fast

• In short, participants saw one of four slide shows:

1. Slow paced, negative statements show

2.2. FastFast paced, negative statements show

3. Slow paced, positive statements show

4.4. FastFast paced, positive statements show

• Thus, the experimenters varied two things:

1. Pace of the slide show (slow or fastfast) and

2. Type of statement (negative or positive)

• For the purpose of this tutorial, imagine that participants rated their mood on the following scale.

Unhappy Happy

• Thus, a darker color represents a darker mood, and a lighter color represents a lighter mood.

Unhappy Happy

InteractionsInteractions

• As you can see from the next slide, this scale allows us to average participants responses without using numbers.

Unhappy Happy

Color 1 Color 2Average of Colors 1 & 2

(Black) (Black) (Black)

(Gray) (Gray) (Gray)

(White) (White) (White)

(Black) (White) (Gray)

• Now, let’s look at some possible results.

• Now, let’s look at some possible results.

• Let’s start with the manipulations having no effect.

Suppose we observed no effect for any of the slide shows: Regardless of condition, everyone ended up in a good (light) mood.

Slow speed Fast speed

Negative Statements

Positive statements

Because type of statement does not matter, we could combine the results from the negative and positive statements, like this:


Negative statements and positive statements

Alternatively, because presentation speed does not matter, we could combine (collapse) the results from the slow and fast statements, like this:

Slow and fast presentations

Negative statements

Positive statements

Finally, because neither presentation speed nor statement type matter, we could combine (collapse) the results into one box, like this:



Suppose we observed no effect for any of the slide shows: Regardless of condition, everyone ended up in a bad (dark) mood.


Negative Statements

Positive statements

Because type of statement does not matter, we could combine (collapse) the results from the negative and positive statements, like this:



Alternatively, because presentation speed does not matter, we could collapse the results from the

slow and fast statements, like this:


Negative statements

Positive statements

Suppose we observed no effect for any of the slide shows: Regardless of condition, everyone ended up in a neutral (gray) mood.


Negative Statements

Positive statements

Because type of statement does not matter, we could collapse the results from the negative and positive statements, like this:


Negative and positive statements

Alternatively, because presentation speed does not matter, we could collapse the results from the slow and fast statements, like this:


Negative statements

Positive statements



Negative and

positive statements

• In the next 4 slides, let’s look at the case in which positive statements help mood more than negative statements.

• This would be called a “statement main effect.”

Negative Statements

Positive Statements

Slow and Fast Presentations

Suppose the only effect was that positive statements had a more positive effect on mood than negative statements.(Slide 1 of 4)

Suppose positive statements have a more positive effect on mood than negative statements (Slide 2 of 4)


Negative Statements

Positive statements

Suppose positive statements have a more positive effect on mood than negative statements (Slide 3 of 4)

Slow speed Fast speed Statement Averages

Negative Statements

Positive statements

Negative

Positive

On average, participants getting negative statements are in a darker mood than those getting positive statements, suggestingan effect for statement type.

Suppose positive statements have a more positive effect on mood than negative statements(Slide 4 of 4)

Slow speed Fast speed Statement Averages

Negative Statements

Positive statements

Speed Averages

Negative

FastSlow

Positive

On average, participants getting the slow slide show are in the same mood than as getting the fast show, suggestingno effect for speed of presentation.

• In the next 4 slides, let’s look at the case in which fast presentation of statements boosts mood more than slow presentation of statements.

• This would be called a “presentation speed main effect.”


Speed has the same effect for both positive and negative statements

PositiveStatements

NegativeStatements

Statements presented quickly seem to boost mood more than statements presented slowly (Slide 1 of 4)



Negative Statements

Positive statements


Negative Statements

Positive statements

Average of slow and fast speeds


Slow Fast

On average, participants getting the slow slide show are in the darker mood than those getting the fast show, suggestingan effect for speed of presentation.

Slow speed Fast speed Average for negative and positive statements

Negative Statements

Positive statements

Average of slow and fast speeds


Slow FastDifferent

Sam

e

Negative

Positive

• Now, let’s look at some interactions. In an interaction, a treatment’s effect in one condition is different from its effect in another condition.

• Sometimes, interactions occur because a treatment has one effect in one condition, but the opposite effect in another condition. For example, some medications can have positive effects under certain circumstances, but negative effects under others.

Interaction:


Negative Statements

Positive statements

Mood lightens (+)

Mood darkens (-)

Speeding up the pace improves mood in the negative statements condition,

but worsens mood in the positive statements condition.

Interaction:


Negative Statements

Positive statements

Speeding up the paceworsens mood in the negative statements condition,

but improves mood in the positive statements condition.

Mood lightens (+)

Mood darkens (-)

• Sometimes, interactions occur because a treatment has an effect in one condition, but no effect in another condition.

Interaction:


Negative Statements

Positive statements

Speeding up the pace has no effect on mood in the negative statements condition, but improves mood in the positive statements condition.

Mood lightens (+)

Mood does not change (0)

Interaction:


Negative Statements

Positive statements

Speeding up the pace has no effect on mood in the negative statements condition, but improves mood in the positive statements condition.


Mood lightens (+)

Interaction:


Negative Statements

Positive statements

Speeding up the pace has darkens mood in the negative statements condition, but has no effect on mood in the positive statements condition.


Mood darkens (-)

• Sometimes, interactions occur because a treatment has more of an effect in one condition than in another.

Interaction:


Negative Statements

Positive statements

Speeding up the pace has lightens mood slightly in the negative statements condition, but lightens mood considerably in the positive statements condition.

Mood lightens greatly (++)

Mood lightens slightly (+)

Interaction:


Negative Statements

Positive statements

Speeding up the pace has darkens mood greatly in the negative statements condition, but darkens mood slightly in the positive statements condition.

Mood darkens slightly (-)

Mood darkens greatly (--)