Chapter 11 - Experimental Designs

Question 1

Establishing a Causal Relation

Answer 1

• Association
  – Independent and dependent variables covary
• Temporal precedence
  – Presumed cause (IV) precedes presumed effect (DV)
• Isolation
  – Presumed cause (IV) must be able to affect the presumed effect
  (DV) all by itself (NOT due to another factor – i.e., a nuisance,
  confounding, contaminating, or extraneous variable)
  – Does NOT mean that there is only one cause for any given effect
  (DV) – think “a” cause, not “the” cause

Question 2

Extent of Researcher Interference

Answer 2

Control

Question 3

Extent of Researcher Interference

Answer 3

Control

Question 4

Control is ____

Answer 4

– Important for establishing causality
– Designs vary in degree & forms of control

Question 5

Factors of cause-probing Experiment

Answer 5

– Manipulation of IV(s)
– Random assignment of units to conditions
* Control & experimental
– Measure effects on DV(s)
– Control potential
confounds
– Clarification:
* Sometimes researchers will do a pre-test and post-test on the DV
* Pre-testing not a defining feature of an experiment

Question 6

Factors of cause-probing Quasi-experiment

Answer 6

– Very similar to experiment
– Except: No random assignment
* May use intact or selfselected groups instead
– More likely to measure potential confounds
* Statistical control
– Similar to both experimental & relational designs

Question 7

What was the Hypothesis of the Popcorn Experiment video?

Answer 7

Orville popcorn makes movies more enjoyable.

Question 8

List the below Features of the Popcorn experiment video

– Manipulation (IV/treatment/intervention)?
– DV/outcome?
– Assignment to conditions?
– Other considerations (e.g., nuisance variables)?

Answer 8

– Manipulation (IV/treatment/intervention)?
——The Popcorn
– DV/outcome?
—— Perceived enjoyment (Rated by patrons)
– Assignment to conditions?
—— Quasi-Experiment
– Other considerations (e.g., nuisance variables)?
—— Lifting of the curtain, Temperature variance,

Question 9

Internal Validity

Answer 9

The extent to which causal inferences (e.g., A causes B) are justified by a research design.

Question 10

External Validity

Answer 10

The extent to which the results from a study (e.g.,
a causal relation between A and B) can be applied
to other settings, people, or events.

Question 11

Threats to Validity

Answer 11

History
Maturation
Testing
Selection bias
Mortality (attrition)
Statistical regression (Regression to the mean)
Instrumentation
General observation

Question 12

Threats to Validity with History

Answer 12

Events occurring concurrently with the treatment could cause the observed effect on the DV.

Question 13

Threats to Validity with Maturation

Answer 13

Naturally occurring changes over time could
be confused with a treatment effect.

Question 14

Threats to Validity with Testing

Answer 14

Exposure to a test can affect score on subsequent
exposures to that test, and this could be confused
with a treatment effect.
* Main (pre-test affects post-test)
* Interactive (pre-test affects reaction to the treatment)

Question 15

Threats to Validity with Selection bias

Answer 15

Systematic differences between conditions in
respondent characteristics that could cause any
observed effect.

Question 16

Threats to Validity with Mortality (attrition)

Answer 16

Loss of respondents to treatment or to
measurement can produce spurious effects if the
attrition is systematically correlated with
conditions (members of one group are more likely
to drop out).

Question 17

Threats to Validity with Statistical regression

Answer 17

When units are selected for their extreme scores,
they will often have less extreme scores on
repeated measurements or on other variables.

Question 18

Threats to Validity with Instrumentation

Answer 18

The nature of a measure may change over time or
conditions in a way that could be confused with a
treatment effect.

Question 19

Threats to Validity with General observation

Answer 19

“Factors Affecting the Validity of Experiments” or “Threats to Validity”
* Inclusion of this material is a nice feature of an introductory
research methods text!
* More complete lists of threats to validity are available
elsewhere.

Question 20

Experimental Designs

Answer 20

Basic

Question 21

Experimental Designs

Answer 21

Pretest-posttest

Question 22

Experimental Designs

Answer 22

Switching replications

Question 23

Experimental Designs

Answer 23

Longitudinal

Question 24

Control group considerations

Answer 24

“No treatment” control is not a defining feature
* E.g., New teaching method vs. no teaching at all???
* Use placebos as a last resort (World Medical Association).
– Instead use new vs. standard treatment (both carefully defined)

Question 25

In quasi-experiments, sometimes “___________” is used instead of “control group”

Answer 25

comparison group

Question 26

Lab experiment

Answer 26

An experimental design set up in an artificially contrived setting where controls and manipulations are introduced to establish cause‐and‐effect relationships among variables of interest to the researcher.

Question 27

Field experiment

Answer 27

An experiment done to detect cause‐and‐effect relationships in the natural environment in which events normally occur.

Question 28

Manipulation

Answer 28

How the researcher exposes the subjects to the independent
variable to determine cause‐and‐effect relationships in experimental designs.

Question 29

Control group

Answer 29

The group that is not exposed to any treatment in an experiment.

Question 30

Treatment

Answer 30

The manipulation of the independent variable in experimental designs so as to determine its effects on a dependent variable of interest to the researcher

Question 31

Match groups

Answer 31

A method of controlling known contaminating factors in
experimental studies, by deliberately spreading them equally
across the experimental and control groups, so as not to confound the cause‐and‐effect relationship.

Question 32

Randomization

Answer 32

The process of controlling the nuisance variables by randomly assigning members among the various experimental and control groups, so that the confounding variables are randomly distributed across all groups.

Question 33

Internal validity of experiments

Answer 33

Attests to the confidence that can be placed in the cause‐and‐
effect relationship found in experimental designs.

Question 34

Field experiment

Answer 34

An experiment done to detect cause‐and‐effect relationships in the natural environment in which events normally occur.

Question 35

External validity

Answer 35

The extent of generalizability of the results of a causal study to other field settings.

Question 36

History effects

Answer 36

A threat to the internal validity of the experimental results, when events unexpectedly occur while the experiment is in progress and contaminate the cause‐and‐effect relationship.

Question 37

Maturation effects

Answer 37

A threat to internal validity that is a function of the biological,
psychological, and other processes taking place in the
respondents as a result of the passage of time.

Question 38

Pretest

Answer 38

A test given to subjects to measure the dependent variable before exposing them to a treatment

Question 39

Posttest

Answer 39

A test given to the subjects to measure the dependent variable after exposing them to a treatment.

Question 40

Testing effects

Answer 40

The distorting effects on the experimental results (the posttest scores) caused by the prior sensitization of the respondents to the instrument through the pretest.

Question 41

Mortality

Answer 41

The loss of research subjects during the course of the experiment, which confounds the cause‐and‐effect relationship.

Question 42

Statistical regression

Answer 42

The threat to internal validity that results when various groups in the study have been selected on the basis of their extreme (very high or very low) scores on some important variables

Question 43

Instrumentation effects

Answer 43

The threat to internal validity in experimental designs caused by changes in the measuring instrument between the pretest and the posttest.

Question 44

Selection effects

Answer 44

The threat to internal validity that is a function of improper or
unmatched selection of subjects for the experimental and control groups.

Question 45

Experimental design

Answer 45

A study design in which the researcher might create an artificial setting, control some variables, and manipulate the independent variable to establish cause‐and‐effect relationships.

Question 46

Experimental group

Answer 46

The group exposed to a treatment in an experimental design.

Question 47

Nuisance variable

Answer 47

A variable that contaminates the cause‐and‐effect relationship.

Question 48

Ex post facto experimental design

Answer 48

Studying subjects who have already been exposed to a stimulus and comparing them to those not so exposed, so as to establish cause‐and‐effect relationships (in contrast to establishing cause‐ and‐effect relationships by manipulating an independent variable in a lab or a field setting).

Question 49

Solomon four‐group design

Answer 49

The experimental design that sets up two experimental groups and two control groups, subjecting one experimental group and one control group to both the pretest and the posttest, and the other experimental group and control group to only the posttest.

Question 50

Double‐blind study

Answer 50

A study where neither the experimenter nor the subjects are
aware as to who is given the real treatment and who the placebo.

Question 51

Simulation

Answer 51

A model‐building technique for assessing the possible effects of changes that might be introduced in a system