Psyc300 Chapter 11

What is a basic experimental design

What is a basic experimental design

One independent and one dependent variable

What are complex experimental designs and what are two of them

• Multiple variables

  • Factorial designs: multiple IV

  • Multivariate designs: multiple DV

2×2 between subjects factorial design: how many independent variables does it have

2 because 2 (IV) x 2 (IV) factorial design

• other example: 3×3 factorial design

  • has 2 IV’s because 3 (iv) x 3 (iv) design

    • 2 number 3’s

2×2 between subjects factorial design: how many conditions does it have

• 4 because 2×2 = 4

• other eg, 3×3 design

  • has 9 conditions because 3×3 = 9

2×2 between subjects factorial design: how many levels does it have

2 levels for IV1 and 2 levels for IV2

• other example

  • 3×3 = 3 levels for IV1, 3 levels for IV2

  • 3×4 = 3 levels for IV1, 4 levels for IV2

why is 2×2 between subjects factorial design a between subjects design

Different participants in the various conditions

what is a confirmatory hypotheses

 the researcher specifies what effects they expect to find

• based on prior knowledge

• predicts the outcome of a specific relationship or phenomenon

• tested through carefully designed experiments or studies

• goal is to validate or confirm what is already believed to be true.

what is an exploratory hypotheses

The researcher does not specify what results will be found 

• discovering new relationships or patterns.

• formed when there is limited existing knowledge about a phenomenon.

• generate new ideas, insights, or theories by exploring the data without a specific prediction in mind.

• gain a better understanding of the subject and to formulate new, testable hypotheses.

what effects do factorial designs have

• main effects

• interaction effects

another name for IV

categorial predictor and factor

what is a main effect

individual influence of each independent variable on the dependent variable, without considering the other independent variables.

what is an interaction effect

effect of one independent variable on the dependent variable depends on the level of another independent variable.

• combined effect of independent variables

• An effect of one IV on the DV depending on the level of the other IV.

factorial design interaction effects graph meanings (how do u plot them, lines crossing, lines not crossing not parallel, lines not crossing but parralel)

• plot the cells mean then make a line of best fit

• lines crossing = interaction

  • opposite effect of variable on dependent variable because of other variable

• line not crossing + non parallel = interaction

  • Effect is exaggerated for one predictor on outcome than other predictor

• lines not crossing + parallel = NOT interaction

  • IV isn’t influenced by other IV

when IV has more then two levels for IV (3×4): main effect

A main effect does not clarify which levels differ

what is a post hoc test

used when factorial has more then 2 levels for IV

• allow researchers to compare the means of the levels of the IV 

Higher-Order Factorial Designs: Effects

A 2 x 2 x 2 higher-order design has three main effects, three two-way interactions, and one three-way interaction. More complex higher-order designs with four or more independent variables are rare

 

Higher-Order Factorial Designs: Plots

Three-way interaction plots often visualize the effect of two variables at the level of a third variable in different plots.

what is repeated measures complex design, what does is increase, and what should we be careful of

• Participants are exposed to all levels of the independent variable 

• Increased statistical power

• Be wary of order effects, interference effects, fatigue, and other confounds

what is a mixed design and give an example

• Includes between-subjects and repeated-measures design features

  • We randomly assign participants to study in either a re-reading or retrieval practice condition and have all participants take a test in a hot and cold room.

  • This is a 2 (Between factor: re-reading or retrieval practice study method) x 2 (Within factor: hot and cold room temperature) between-within mixed design

how many participants do complex designs, interaction effects and smaller effects need and why

• Complex designs require more participants for appropriate power 

• Interaction effects require more participants than main effects

• Smaller effects require more participants 

what should researchers focus on when conducting a study

focus on conducting larger, well-powered studies