Psc 41 Exam 2

Front 1

What we need to control.

Front 2

What is a confound?

Back 2

some extraneous variable or flaw in the experiment.

Front 3

What is internal validity? What are the threats to internal validity?

Back 3

the degree to which the results of an experiment are due to the experimental manipulation of the independent variable and rather than to some cofounding variable. • Nonequivalent control group - best way to avoid is by random sampling • History effect - an outside event that is not part of the experimental manipulation may have caused the results. • Maturation effect - naturally occurring changes within the participants could be responsible for the observed changes in the dependent variable • Testing effects repeated testing could lead to better or worse scores. examples are Practice and Fatigue effects • Regression to the mean - extreme scores upon retesting tend to be less extreme, that is they move close to the mean. • Instrumentation - changes in the dependent variable are due to changes in the measuring instrument. Think faulty device. •Mortality and attrition - dropout • Diffusion of treatment - observed changes in the current participants’ performance may be due to information received from people who had participated in the experiment in the past. • Experimenter and participant effects - the experimenter or participant consciously or unconsciously affects the results of the study. Control by blinded studies • Floor effect – a limitation of the measuring instrument that decreases its ability to detect differences between scores at the bottom of the scale • Ceiling effect – a limitation of the measuring instrument that decreases its ability to differentiate between scores at the top of the scale

Front 4

What are the threats to external validity? How can these threats be overcome?

Back 4

the extent to which the results of an experiment can be generalized. Threats are Generalization to populations – “College Sophomore Problem” – most research participants are college Freshmen or Sophomore, this is not necessarily a representative sample of the population, therefore making it difficult to generalize. • Generalization from Laboratory Settings – conducting research in a laboratory setting creates an artificial environment. In turn, we have to exercise caution when making generalizations from a laboratory setting. Ways of overcoming this issue: 1.) Exact replication – repeat the study exactly 2.) Conceptual replication – test the same concepts in a different way 3.) Systematic replication – systematically change one part of the experiment at a time and observe the effect

Front 5

Between-participants design

Front 6

Posttest-only control group design

Back 6

Between participants test - dependent variable is measured AFTER the independent variable is administered.

Front 7

Experimenter effect

Front 8

Correlated-groups design

Back 8

the participants in the experimental and control groups are related. 2 types: within participants design and Matched-participants experimental design

Front 9

Pretest/posttest control group design

Back 9

type of between participants
dependent variable is measured both before and after the
independent variable is administered.
• Disadvantages of this design: may increase demand
characteristics and experimenter effects.

Front 10

Single-blind experiment

Front 11

Within-participants design

Back 11

same participants are used in each condition. Advantages: • Randomly recruit participants but don’t need random assignment because all participants will partake in both conditions. • Typically requires fewer participants than between participants design. • Requires less time to conduct • Increases statistical power. When the same individuals participate in multiple conditions, individual differences between conditions are minimized. This reduces variability and increases the chance to reach statistical significance. Disadvantages: • Internal validity is a concern. • Order effects (another type of testing effect) are of concern because all participants are measured at least twice, so the order in which the conditions are presented may have an effect on the dependent variable. • Practice and Fatigue effects • Counterbalancing , systematically varying the order of the conditions for participants in a within-participants design, can control for these potential confounding effects. • Internal validity is a concern. • Carryover effects – participants ‘carry’ something over with them from one condition to another. That is, what the participants learned (or experienced) in one condition may be carried over with them to the next condition, in turn influencing their performance. Counterbalancing could also help control carryover effects. • Demand characteristics (the info the participant infers the researcher wants) – since the participants partake in both conditions they have access to more information regarding the study, which can influence their performance.

Front 12

Matched-participants experimental design

Back 12

• This is a cross between the between- and within-participants designs. • In this design not all participants partake in each condition. Like the between-participants design, half the participants are assigned to the experimental condition and the other half to the control condition. • However, for each participant in one condition, there is another participant in the other condition that matches him/her on the relevant variables. 23 Advantages: • Eliminates carryover effects. • Minimizes testing effects and demand characteristics • The groups are more equivalent than those in the between-participant design and almost as equivalent as those in the within-participant design • Because the participants have been matched on the variable(s) of interest, the same statistics used for the within-participants design can be used on the matchedparticipants design. 24 The Logic of Experimental Design Correlated-Group Designs: • Matched-participants experimental design Disadvantages: • More participants are needed than in the withinparticipants design. • If one participant drops out, the entire pair is lost. • Matching participants can be VERY difficult.

Front 13

Developmental Designs:

Back 13

use age as a variable. • 3 main types: 1.) Cross-sectional design 2.) Longitudinal design 3.) Sequential design

Front 14

Cross-sectional design

Back 14

• Participants of different ages are studied at the same time. Advantage: • Fast – a wide variety of ages can be studied in a short period of time. Disadvantage: • Cohort effects – (cohort = a group of individuals born at the same time) – With the cross-sectional design the researcher wants to conclude that any observed difference are due to age, but they could also be due to cohort effects, the differences that may arise because the people were raised at different times and in different generations (or cohorts).

Front 15

Longitudinal design

Back 15

• The same participants are studied repeatedly over time (follow the participants over time). Advantage: • No cohort effects Disadvantage: • Expensive • Time consuming • Attrition

Front 16

Sequential design

Back 16

• Combination of the cross-sectional and longitudinal designs. • Researcher begins with participants of differing ages (crosssectional design) and tests or measures them. And then follows them over a period of time (longitudinal design). Advantage: • Allows researchers to examine cohort effects. Disadvantage: • More expensive and time consuming than the previous two designs. • Attrition

Front 17

What are some threats to internal validity?

Back 17

1.) nonequivalent groups, 2.) history effect, 3.) maturation effect, 4.) testing effect, 5.) regression to the mean, 6.) instrumentation effect, 7.) mortality or attrition, 8.)diffusion of treatment, 9.) experimenter and participant effects, and 10.) floor and ceiling effects.

Front 18

What are some threats to external validity?

Back 18

1.) generalization to populations, and 2.) generalization from laboratory settings.

Front 19

Confound

Back 19

extraneous variable or flaw in
the experiment.

Front 20

Double-blind experiment

Back 20

Neither knows what is going on

Front 21

Order effects

Back 21

the order in which the conditions are presented have an effect on the dependent variable.

Front 22

What are some advantages of the within subject design? Disadvantages?

Back 22

Advantages: Fewer participants are needed, less time-consuming, equivalency of groups is ensured, more powerful statistically. Disadvantages: Probability of testing effects is high, probability of demand characteristics is high.

Front 23

What is a disadvantage(s) of the longitudinal design?

Back 23

1.) time consuming, 2.) expensive, and 3.) attrition

Front 24

What is a sequential design?

Back 24

A type of developmental design that is a combination of the cross-sectional and longitudinal designs. • Researcher begins with participants of differing ages (crosssectional
design) and tests or measures them. And then
follows them over a period of time (longitudinal design).
Advantage:
• Allows researchers to examine cohort effects.
Disadvantage:
• More expensive and time consuming than the previous two
designs.
• Attrition

Front 25

Participant effect

Back 25

participant consciously or unconsciously affects the results of the study.

Front 26

Counterbalancing

Back 26

systematically varying the order of the conditions for participants in a within-participants design, can control for these potential confounding effects.

Front 27

History effect

Back 27

Changes in the dependent variable may be due to outside events that take place during the course of the study. (ie depression and 911)

Front 28

Placebo group

Back 28

a group which does not receive the ‘real drug, but rather receives a ‘fake’ drug under the guise that it is the ‘real drug

Front 29

Matched-participants design

Back 29

the participants are matched between conditions or variables that the experimenter believes are (is) relevant to the study.

Front 30

Maturation effect

Back 30

Changes in the dependent variable may be due to participants maturing (growing older) during the course of the study.

Front 31

Placebo

Back 31

fake drug

Front 32

Cross-sectional design

Back 32

Participants of different ages are studied at the same time.

Front 33

Testing effect

Back 33

Changes in the dependent variable may be due to participants being tested repeatedly and getting either better or worse because of the repeated testing.

Front 34

Floor effect

Back 34

Equipment can't see differences below a certain level

Front 35

Cohort

Back 35

group of individuals born at the same time

Front 36

Regression to the mean

Back 36

extreme scores upon retesting tend to be less extreme, that is they move close to the mean.

Front 37

Cohort effect

Back 37

differences that may arise because the people were raised at different times and in different generations (or cohorts).