Complex Experiments Ch. 11 PDF

**[Complex experiments-ch.11:]** *What are complex experiments?* [Complex experiments:] Studies that have more than one IV and/or two levels of an IV. *What are the benefits of a complex experimental design?* [Benefits and differences:] - Closer to real world phenomena - Examine interacti...

**[Complex experiments-ch.11:]** *What are complex experiments?* [Complex experiments:] Studies that have more than one IV and/or two levels of an IV. *What are the benefits of a complex experimental design?* [Benefits and differences:] - Closer to real world phenomena - Examine interactions - Examine non-linear relationships *In oppose to simple designs in which you can examine simple casual relationships that are only LINEAR.* *Terms:* *Factor = IV* *Level = number of conditions* *How to keep internal validity in complex experimental designs?* [Internal validly in complex experiments:] - Random assignment - Experimental control *How to organize complex designs? According to the factors and levels of the IV.* [**Factorial designs** (organization of complex experiments): ] In the form of a multiplication. Represented in a table. a. The numbers= numbers of factors. b. The values= levels of the IV. c. The multiple= number of conditions Ex: 2 x 3 x 2 factorial design Number of IVs = 3 Levels = 2, 3, 2 Conditions= 12 Features of factorial designs: a. [Main effect:] Effect of one IV on the DV only. b. [Interaction:] Influence of one IV on another IV to cause the DV. If there is an interaction between IVs then we use the term "it depends" to describe effect on DV. c. *[Moderator] = variable that cause interaction.* a. [Cell] [mean:] **average** of DV in **each condition of a level** (in each box/cell) How? Total DV value in each condition / total ps in the condition *Basically, summarizing data of each condition* b. [Marginal mean:] **average** of DV in **all conditions** of **each level of IV**. \*\*Pick one direction of view. How? Add DV of each cell/ total number of cells *Basically, comparing the levels within an IV now* c. [Interaction:] **Difference** between **cells of one level** of IV **due to other levels** of IV. How? subtract the DV value of each condition from its other condition of one factor (IV). Interpretation of calculations: in factorial design a. Cell mean = average of each condition Why? There are multiple entries by ps b. Marginal mean = indicator of a main effect How? 1. Marginal mean different: each level of a factor Result: main effect present 2. Marginal mean equal: each level of a factor Result: no main effect c. Interaction = difference between conditions of each level of a factor Result: 1. Difference is the same value= no interaction \*\*effect of IV1 on DV is constant across all levels of IV2 2. Different are different value= an interaction is present \*\*effect of IV 1 on DV depends on the effect of IV2 on IV1 IV 2 Level 1 Level 2 ------ --------- --------------------------- --------------------------- IV 1 Level 1 [Condition 1] [Condition 2] Level 2 [Condition 3] [Condition 4] [Example: ] Effect of music on focusing. Music= IV1. Level 1: rock music Level 2: classical music Effect of visual pictures on focusing. Pictures=IV2. Level 1: coloured picture Level 2: black and white picture DV = Score on a comprehension quiz from focusing on the content (out of 10) Total ps=8 Coloured Black & white Marginal mean --------------- ---------- --------------- --------------- Rock 4 6 5 Classical 7 8 7.5 Marginal mean 5.5 7 1. Split ps = 4/condition. (8/level) 2. Ps scores: 2.4 3.7. in condition Rock and coloured 3. Cell mean ? 16/4= 4 4. Marginal mean? \*\* [choose perspective= IV1] Level of Rock: coloured or B&W average= 10/2 = 5 Level of classical: coloured or B&W average= 15/2= 7.5 Is there a main effect? YES. Because the DV is different at each level of IV1. 5. Interaction? Difference of each level of IV1: (perspective IV1) Rock = 2 Classical = 1 2 is not equal to 1 so there is an interaction. (It depends!) Influence of music on focusing depends on the type of picture exposed to. Effect of type of music on score of the quiz depends on type of picture exposed to.