Chapter 10: Intro to Simple Experiments

Question 1

What is an ‘experiment?’

Answer 1

A study in which at least one variable is manipulated, and another is measured. Take place anywhere the researcher can manipulate one variable and measure another.

Question 2

What is a ‘manipulated variable?’

Answer 2

A variable in an experiment that a researcher controls, such as by assigning participants to its different levels (values).

Question 3

What is a ‘measured variable?’

Answer 3

A variable in a study whose levels (values) are observed and recorded.

Question 4

What are examples of ‘manipulated variables?’

Answer 4

A controlled variable can be when a researcher assigns participants to a particular level (value) of the variable. The participants do not get to choose which value.

Question 5

What are examples of a ‘measured variable?’

Answer 5

It can take the form of records of behaviour or attitudes, such as self-reports, behavioural observations, or recorded physiological measures.

Question 6

What is an ‘independent variable?’

Answer 6

In an experiment, a variable that is manipulated. In a multiple-regression analysis, a predictor variable is used to explain variance in the criterion variable.

Question 7

What are ‘conditions?’

Answer 7

One of the levels of the independent variable in an experiment.

Question 8

What is a ‘dependent variable?’

Answer 8

In an experiment, the variable that is measured. In a multiple-regression analysis, the single outcome or criterion variable the researchers are most interested in understanding or predicting.

Question 9

What is a ‘control variable?’

Answer 9

In an experiment, a variable that a researcher holds constant on purpose. Not really a variable at because they do not vary in an experiment; experimenters keep the levels the same for all participants.

Question 10

What is the purpose of the ‘control variable?’

Answer 10

Control variables enhance the internal validity of a study by limiting the influence of confounding and other extraneous variables. This helps you establish a correlational or causal relationship between your variables of interest.

Question 11

What are the minimum requirements for a study to be an experiment?

Answer 11

Require a manipulated variable and a measured variable.

Question 12

What is ‘covariance?’

Answer 12

Covariance measures the direction of the relationship between two variables. A positive covariance means that both variables tend to be high or low at the same time. A negative covariance means that when one variable is high, the other tends to be low.

Question 13

What is ‘temporal precedence?’

Answer 13

• Establishing that the cause (i.e., independent variable) occurs before the effect (i.e., outcome);
• Establishing that the cause and effect are related and/or covary; and.
• Establishing that there are no plausible alternative explanations.

Question 14

Whare the three rules for causation?

Answer 14

1. Covariance
2. Temporal precedence
3. Internal validity

Question 15

What is ‘internal validity?’

Answer 15

Refers to whether the effects observed in a study are due to the manipulation of the independent variable and not some other factor.

Question 16

What is a ‘comparison group?’

Answer 16

A group in an experiment whose levels on the independent variable differ from those of the treatment group in some intended and meaningful way. Also called the comparison condition.

Question 17

What is a ‘control group?’

Answer 17

A level of an independent variable that is intended to represent “no treatment” or a neutral condition. Also called control condition.

Question 18

What is a ‘treatment group?’

Answer 18

The participants in an experiment who are exposed to the level of the independent variable that involves a medication, therapy, or intervention.

Question 19

What is a ‘placebo group?’

Answer 19

A control group in an experiment that is exposed to an inert treatment, such as a sugar pill. Also called the placebo control group.

Question 20

What is a ‘confound?’

Answer 20

A general term for a potential alternative explanation for a research finding; a threat to internal validity.

Question 21

What is a ‘design confounds?’

Answer 21

A threat to internal validity in an experiment in which a second variable happens to vary systematically along with the independent variable and therefore is an alternative explanation for the results.
- A mistake redesigning the independent variable; it occurs when a second variable happens to vary systematically along with the intended independent variable.

Question 22

What is ‘systematic variability?’

Answer 22

In an experiment, a description of when the levels of a variable coincide in some predictable way with experimental group membership creates a potential confound.
- Introduces a confound

Question 23

What is ‘unsystematic variability?’

Answer 23

In an experiment, a description of when the levels of a variable fluctuate independently of experimental group membership, contributeing to variability within groups.

Question 24

What are ‘selection effects?’

Answer 24

A threat to internal validity that occurs in an independent-groups design when the kinds of participants at one level of the independent variable are systematically different from those at the other level.

Question 25

What is ‘random assignment?’

Answer 25

The use of a random method (e.g. flipping a coin) to assign participants into different experimental groups.

Question 26

What are ‘matched groups’?

Answer 26

An experimental design technique in which participants who are similar on some measured variable are grouped into sets; the members of each matched set are then randomly assigned to different experimental conditions. Also called, matching.

Question 27

How does using matched groups prevent selection effects?

Answer 27

Matching has the advantage of randomness. Because each member of the matched pair is randomly assigned (which prevents selection effects). This method also ensures that the groups are equal on some important variable before the manipulation of the independent variable.

Question 28

How are design confounds and control variables related?

Answer 28

Control variables are used to eliminate potential design confounds. In which different groups of participants are placed into different levels of the independent variable. Also called between-subjects or between-groups desig

Question 29

Independent-groups design / Between-subjects design / Between-groups design

Answer 29

An experimental design in which different groups of participants are exposed to different levels of the independent variables, such that each participant experiences only one level of the independent variable.

Question 30

Within-group design

Answer 30

An experimental design in which each participant is presented with all levels of the independent variable.
- Within-groups designs require fewer participants

Question 31

Posttest-only design / Equivalent groups, posttest-only design

Answer 31

An experiment using an independent-groups design in which participants are tested on the dependent variable only once.

Question 32

Pretest/posttest design / equivalent groups pretest/posttest design

Answer 32

An experiment using an independent-groups design in which participants are tested on the key dependent variable twice: one before and one after exposure to the independent variable.

Question 33

What is the difference between independent-groups and within-groups designs? Use te term levels in your answer.

Answer 33

Independent groups are situations where each participant only sees one level of the IV. That is each level if the IV are independent from each other. Within group design is when each participant experiences all levels of the IV. Explain the difference between concurrent- measures and repeated measures designs.

Question 34

Describe why posttest-only and pretest/posttest designs are both independent-group designs. Explain how they differ.

Answer 34

posttest only: participants are randomly assigned to independent variable groups and are tested on the dependent variable once. Satisfy all three criteria. They allow researchers to covariance by detecting differences in the dependent variable. they establish temporal precedence because the independent variable comes first in time. They establish internal validity.
Pretest/posttest designs: participants are randomly assigned to at least two groups. They are tested on the key dependent variable twice: once before and once after exposure to the independent variable. Researchers might use a pretest/posttest design to evaluate whether random assignments equalled the groups.

Question 35

Repeated-measures design

Answer 35

An experiment using a within-groups design in which participants respond to a dependent variable more than once after exposure to each level of the independent variable.

Question 36

Concurrent-measures design

Answer 36

An experiment using a within-groups design in which participants are exposed to all levels of an independent variable at roughly the same time, and a single attitudinal or behavioural preference is the dependent variable.

Question 37

Order effects

Answer 37

In a within-groups design, a threat to internal validity in which exposure to one condition changes participant responses to a later condition.

Question 38

Practice effect / fatigue effect

Answer 38

A type of order effect in which participants’ performance improves over time because they become practiced at the dependent measure (not because of the manipulation or treatment).

Question 39

Carryover effect

Answer 39

A type of order effect in which some form of contamination carries over from one condition to the next.

Question 40

Counterbalancing

Answer 40

In a repeated-measures experiment, we present the level of the independent variable to participants in different sequences to control for order effects.

Question 41

Full counterbalancing

Answer 41

A method of counterbalancing in which all possible condition orders are represented.

Question 42

Partial counterbalancing

Answer 42

A method of counterbalancing in which some, but not all, of the possible condition orders, are represented.

Question 43

Latin Square

Answer 43

A formal system of partial counterbalancing ensures that every condition in a within-groups design appears in each position at least once.

Question 44

Demand Characteristics

Answer 44

A cue that leads participants to guess a study’s hypotheses or goals; is a threat to internal validity.

Question 45

Is a pretest/posttest repeated measures design?

Answer 45

• In a true repeated-measure design, participants are exposed to all levels of a meaningful independent variable. The levels can be counterbalanced.
• In a pretest/posttest design, participants can only see one level of the independent variable, not all levels.

Question 46

Manipulation Check

Answer 46

In an experiment, an extra dependent variable researchers can include to determine how well a manipulation worked.

Question 47

Pilot Study

Answer 47

A study completed before (or sometimes after) the study of primary interest, usually to test the effectiveness or characteristics of the manipulations.

Question 48

How do manipulation checks provide evidence for the construct validity of an experiment’s independent variable? Why does theory matter in evaluating construct validity?

Answer 48

manipulation check is an additional DV (dependent variable) that researchers can insert into an experiment to help them quantify how well an experimental manipulation worked.

Theory matters in evaluating construct validity to see if the measures you used will be testing the right things so you do not get results that don’t answer your question

Question 49

Besides generalization to other people, what other aspect of generalization does external validity address?

Answer 49

generalization to other situations

Question 50

What does it mean when an effect size is large (as opposed to small) in an experiment?

Answer 50

The causal effect is stronger or more important.

the independent variable caused the dependent variable to change for more of the participants in the study

Question 51

Summarize three threats to internal validity discussed in this chapter:

Answer 51