Chapter 10: Simple Experiments

Question 1

Experiment

Answer 1

Researchers manipulated at least one variable and measured another
Can take place anywhere that variables can be manipulated and measured

Question 2

Manipulated Variable

Answer 2

Variable that is controlled
Levels created by researcher

Question 3

Measured Variable

Answer 3

Record behaviour or attitudes
Self reports, behavioural observations, or physiological measures
Recording what happens after selecting manipulated variables

Question 4

Independent Variable

Answer 4

Manipulated (causal) variable
Researcher has independence in assigning people to levels of it
Independent variable should not be confused with its levels (referred to as conditions)
On x axis
E.g. emotion (anger, happiness, neutral responses to offer)
E.g. methods of note taking (paper, computer)

Question 5

Dependent Variable

Answer 5

Outcome variable
How participant acts on the measured variable depends on the level of independent variable
Less control over dependent
Y axis

Question 6

Control Variable

Answer 6

Variable that an experimenter holds content on purpose
Need to ensure manipulating only one thing at a time
Crucial for internal validity
E.g. watch lecture in same room, same experimenter, same video, same questions

Question 7

Criteria for Causal Claims

Answer 7

Covariance: do results show that the causal variable is related to the outcome variable
Temporal precedence: design ensures causal variable comes before outcome variable
Internal validity: design rules out alternative explanations for the results

Question 8

Covariance

Answer 8

No difference in dependent variable between the manipulations = no covariance
Comparison groups allows comparison between levels of variables and their outcomes (establishes covariance)
All experiments need comparison group (doesn’t have to be a control group)

Question 9

Control Group

Answer 9

Level of independent variable intended to represent ‘no treatment’ or neutral condition

Question 10

Treatment Group

Answer 10

Other levels of independent variable aside from control

Question 11

Placebo Group

Answer 11

When control group is exposed to inert treatment

Question 12

Confound

Answer 12

Possible alternative explanations (threats to internal validity)

Question 13

Design Confound

Answer 13

Experimenter’s mistake in designing the independent variable
Second variable happens to vary systematically along with the intended independent variable
Accidental second variable is alternative explanation
E.g. if all written notetakers were more interested in lecture than computer notetakers

Question 14

Selection Effects

Answer 14

Result when kinds of participants in one level of independent variable are systematically different from those in the other
Can also happen when experiments let participants choose which group they want to be in (e.g. ask which note taking method people want to use)
Can also happen when researchers assign one type of person to first condition and another type to second condition (e.g. assigning all women or all people who sign up early to one condition)
E.g. families assigned to intensive therapy for autism condition were more eager to make it happen, lived closer, etc
Avoid with random assignment and matched groups

Question 15

Random Assignment

Answer 15

Each participant has equal chance of being in each condition
This divides certain types of people more equally
Controls for selection effects

Question 16

Matched Groups

Answer 16

Measure participants on particular variable that might matter to dependent variable (e.g. student achievement (GPA) could matter for note taking experiment)
Match participants in pairs based on similarity (e.g. two highest GPAs)
Within matched sets randomly assign conditions
Prevents selection effects (ensures equal groups)

Question 17

Independent Groups Design

Answer 17

Separate groups of participants are placed into different levels of the independent variable
Also called between-subjects or between-groups design
Posttest-only design & pretest-posttest design

Question 18

Within-Groups Design

Answer 18

Each person is presented with all levels of the independent variable
Also called within-subjects design
Concurrent-measures design & repeated-measures design

Question 19

Posttest-Only Design

Answer 19

AKA equivalent groups, post-test-only design
Participants randomly assigned to independent variable groups
Tested on the dependent variable once
E.g. note taking study, knowledge tested only once
Satisfies causation criteria

Question 20

Pretest/Posttest Design

Answer 20

AKA equivalent groups, pretest/posttest design
Tested on the dependent variable once before and once after exposure to the independent variable
E.g. test vocal score before and after two week mindfulness class
When want to ensure groups are equal or study improvement over time

Question 21

Repeated-Measures Design

Answer 21

Participants measured on a dependent variable more than once, after exposure to each level of independent variable
E.g. Participants experienced both levels: tasting chocolate together and tasting it while confederate was looking at painting
Each participant rated the chocolate twice (told it was different even though was the same)

Question 22

Concurrent-Measures Design

Answer 22

Participants exposed to all levels of independent variable at roughly the same time
Single attitudinal behaviour preference is dependent variable
E.g. babies shown faces (male and female) at same time to see which look at longer
Levels were male and female faces, exposed at the same time
Behavioural preference was looking preference (dependent)

Question 23

Order Effects

Answer 23

Within-group designs
Being exposed to one condition first changes how participants react to the later condition (confound)
Avoid by counterbalancing

Question 24

Practice Effects

Answer 24

Within-group designs
Fatigue effects
Long sequence might lead participants to get better at the task or to get tired or bored toward the end

Question 25

Carryover Effects

Answer 25

Within-groups designs
Contamination carries over from one condition to the next
E.g. first bite of chocolate is always better than later bites

Question 26

Counterbalancing

Answer 26

Present the levels of the independent variable to participants in different sequences
Any order effects should cancel each other out when data are combined

Question 27

Full Counterbalancing

Answer 27

When a within-groups experiment has only two or three levels of independent variable
All possible condition orders are represented
Can cause an increased need for participants

Question 28

Partial Counterbalancing

Answer 28

Only some of the possible condition orders are represented
Present conditions in randomized order for every subject
Latin square: formal system to ensure that every condition appears in each position at least once

Question 29

Manipulation Check

Answer 29

Extra dependent variable that researchers insert into an experiment to convince them that their experimental manipulation worked
More likely to be used when intention is to make participants think or feel certain ways
E.g. researchers manipulate feelings of anxiety by telling some students they have to give a speech
Manipulation check can determine is operationalization of anxiety worked as intended
Tests construct validity

Question 30

Pilot Study

Answer 30

Simple study using a separate group of participants
Completed before or sometimes after the study of primary interest
To confirm effectiveness of the manipulations
Tests construct validity