This document summarizes key concepts related to experimental and correlational research methods. It discusses the major features of experimental research, including manipulating an independent variable and measuring dependent variables. It also covers correlational research, validity types (construct, internal, external), measurement considerations, and the tradeoff between internal and external validity when generalizing from lab studies.
Experimental and Quasi-Experimental DesignsChapter 5.docxelbanglis
Experimental and Quasi-Experimental Designs
Chapter 5
*
Introduction
Experiments are best suited for explanation and evaluation research
Experiments involve:
Taking action
Observing the consequences of that action
Especially suited for hypothesis testing
Often occur in the field
The Classical Experiment Classical experiment: a specific way of structuring researchInvolves three major components:
Independent variable and dependent variable
Pretesting and posttesting
Experimental group and control group
Independent and Dependent Variables
The independent variable takes the form of a dichotomous stimulus that is either present or absent
It varies (i.e., is independent) in our experimental process
The dependent variable is the outcome, the effect we expect to see
Might be physical conditions, social behavior, attitudes, feelings, or beliefs
Pretesting and Posttesting
Subjects are initially measured in terms of the DV prior to association with the IV (pretested)
Then, they are exposed to the IV
Then, they are remeasured in terms of the DV (posttested)
Differences noted between the measurements on the DV are attributed to influence of IV
Experimental and Control Groups
Experimental group: exposed to whatever treatment, policy, initiative we are testing
Control group: very similar to experimental group, except that they are NOT exposed
Can involve more than one experimental or control group
If we see a difference, we want to make sure it is due to the IV, and not to a difference between the two groups
Placebo
We often don’t want people to know if they are receiving treatment or not
We expose our control group to a “dummy” independent variable just so we are treating everyone the same
Medical research: participants don’t know what they are taking
Ensures that changes in DV actually result from IV and are not psychologically based
Double-Blind Experiment
Experimenters may be more likely to “observe” improvements among those who received drug
In a double-blind experiment, neither the subjects nor the experimenters know which is the experimental group and which is the control group
Selecting Subjects
First, must decide on target population – the group to which the results of your experiment will apply
Second, must decide how to select particular members from that group for your experiment
Cardinal rule – ensure that experimental and control groups are as similar as possible
RandomizationRandomization: produces an experimental and control group that are statistically equivalentEssential feature of experimentsEliminates systematic bias
Experiments and Causal Inference
Experimental design ensures:
Cause precedes effect via taking posttest
Empirical correlation exists via comparing pretest to posttest
No spurious 3rd variable influencing correlation via posttest comparison between experimental and control groups, and via randomization
Example of Research Using an Experimental Design
Researchers at the University of Marylan ...
Experimental and Quasi-Experimental DesignsChapter 5.docxelbanglis
Experimental and Quasi-Experimental Designs
Chapter 5
*
Introduction
Experiments are best suited for explanation and evaluation research
Experiments involve:
Taking action
Observing the consequences of that action
Especially suited for hypothesis testing
Often occur in the field
The Classical Experiment Classical experiment: a specific way of structuring researchInvolves three major components:
Independent variable and dependent variable
Pretesting and posttesting
Experimental group and control group
Independent and Dependent Variables
The independent variable takes the form of a dichotomous stimulus that is either present or absent
It varies (i.e., is independent) in our experimental process
The dependent variable is the outcome, the effect we expect to see
Might be physical conditions, social behavior, attitudes, feelings, or beliefs
Pretesting and Posttesting
Subjects are initially measured in terms of the DV prior to association with the IV (pretested)
Then, they are exposed to the IV
Then, they are remeasured in terms of the DV (posttested)
Differences noted between the measurements on the DV are attributed to influence of IV
Experimental and Control Groups
Experimental group: exposed to whatever treatment, policy, initiative we are testing
Control group: very similar to experimental group, except that they are NOT exposed
Can involve more than one experimental or control group
If we see a difference, we want to make sure it is due to the IV, and not to a difference between the two groups
Placebo
We often don’t want people to know if they are receiving treatment or not
We expose our control group to a “dummy” independent variable just so we are treating everyone the same
Medical research: participants don’t know what they are taking
Ensures that changes in DV actually result from IV and are not psychologically based
Double-Blind Experiment
Experimenters may be more likely to “observe” improvements among those who received drug
In a double-blind experiment, neither the subjects nor the experimenters know which is the experimental group and which is the control group
Selecting Subjects
First, must decide on target population – the group to which the results of your experiment will apply
Second, must decide how to select particular members from that group for your experiment
Cardinal rule – ensure that experimental and control groups are as similar as possible
RandomizationRandomization: produces an experimental and control group that are statistically equivalentEssential feature of experimentsEliminates systematic bias
Experiments and Causal Inference
Experimental design ensures:
Cause precedes effect via taking posttest
Empirical correlation exists via comparing pretest to posttest
No spurious 3rd variable influencing correlation via posttest comparison between experimental and control groups, and via randomization
Example of Research Using an Experimental Design
Researchers at the University of Marylan ...
20. (8` points) Two observers observe a child in the classro.docxlorainedeserre
20. (8` points) Two observers observe a child in the classroom every 30 minutes to record whether he is behaving aggressively. They use two categories for their observations: yes (aggressive) or no (not aggressive). Using the data presented below, answer the following question.
Calculate and report the observers' interobserver reliability.
Do you think the observers demonstrated acceptable interobserver reliability? Why or why not?
21. (5 points) A researcher was interested in determining whether more frequent breaks (i.e., "coffee breaks") in a business setting would help employees to be more productive. With the cooperation of the management, employees on one floor of the corporate offices were allowed to take a 10-minute break each hour (at any time) between 8:00 and 11:00 A.M. (for a total of 30 minutes). The comparison group comprised employees on different floors who followed the usual corporate policy of taking a 30-minute break sometime during the morning (at any time). Measures of productivity were gathered for each employee according to his or her job (e.g., number of reports written, number of sales made, etc.). A time series analysis was applied to compare the productivity of both groups of employees for six months before and after the intervention (started in July). Quite surprisingly, the productivity of both groups increased following the onset of the intervention, suggesting to the researcher that the timing of breaks makes no difference.
What type of research design was used in this study?
Describe two ways in which contamination may have influenced the results of this study.
Describe one threat to internal validity that might be present in this study because the independent variable manipulation was implemented on different floors of the building.
Research Methods in Psychology
Quasi-Experimental Designs
1
Characteristics of True Experiments
Manipulate Independent Variable (IV)
Treatment, comparison conditions
High degree of control
Choice of the DVs
Random assignment to conditions
Unambiguous outcome regarding effect of IV on DV
Internal validity
2
Applied Research
Goals
Test external validity of lab findings
Improve conditions in which people live and work (natural settings)
Quasi-experiments
Procedures that approximate the conditions of highly controlled laboratory experiments
3
Permission
Difficult to gain permission to conduct true experiments in natural settings
Difficult to gain access to participants
Random assignment perceived as unfair
People want a “treatment”
Random assignment is best way to determine whether a treatment is effective
Use “waiting-list” control group or alternate treatments
Tablets in English and science classes example
Obstacles to Conducting True Experiments in Natural Settings
4
Advantage of True Experiments
Threats to internal validity are controlled
8 general threats to internal validityhistoryregressionmaturationselectiontestingsubject attritionin ...
Ethnobotany and Ethnopharmacology:
Ethnobotany in herbal drug evaluation,
Impact of Ethnobotany in traditional medicine,
New development in herbals,
Bio-prospecting tools for drug discovery,
Role of Ethnopharmacology in drug evaluation,
Reverse Pharmacology.
20. (8` points) Two observers observe a child in the classro.docxlorainedeserre
20. (8` points) Two observers observe a child in the classroom every 30 minutes to record whether he is behaving aggressively. They use two categories for their observations: yes (aggressive) or no (not aggressive). Using the data presented below, answer the following question.
Calculate and report the observers' interobserver reliability.
Do you think the observers demonstrated acceptable interobserver reliability? Why or why not?
21. (5 points) A researcher was interested in determining whether more frequent breaks (i.e., "coffee breaks") in a business setting would help employees to be more productive. With the cooperation of the management, employees on one floor of the corporate offices were allowed to take a 10-minute break each hour (at any time) between 8:00 and 11:00 A.M. (for a total of 30 minutes). The comparison group comprised employees on different floors who followed the usual corporate policy of taking a 30-minute break sometime during the morning (at any time). Measures of productivity were gathered for each employee according to his or her job (e.g., number of reports written, number of sales made, etc.). A time series analysis was applied to compare the productivity of both groups of employees for six months before and after the intervention (started in July). Quite surprisingly, the productivity of both groups increased following the onset of the intervention, suggesting to the researcher that the timing of breaks makes no difference.
What type of research design was used in this study?
Describe two ways in which contamination may have influenced the results of this study.
Describe one threat to internal validity that might be present in this study because the independent variable manipulation was implemented on different floors of the building.
Research Methods in Psychology
Quasi-Experimental Designs
1
Characteristics of True Experiments
Manipulate Independent Variable (IV)
Treatment, comparison conditions
High degree of control
Choice of the DVs
Random assignment to conditions
Unambiguous outcome regarding effect of IV on DV
Internal validity
2
Applied Research
Goals
Test external validity of lab findings
Improve conditions in which people live and work (natural settings)
Quasi-experiments
Procedures that approximate the conditions of highly controlled laboratory experiments
3
Permission
Difficult to gain permission to conduct true experiments in natural settings
Difficult to gain access to participants
Random assignment perceived as unfair
People want a “treatment”
Random assignment is best way to determine whether a treatment is effective
Use “waiting-list” control group or alternate treatments
Tablets in English and science classes example
Obstacles to Conducting True Experiments in Natural Settings
4
Advantage of True Experiments
Threats to internal validity are controlled
8 general threats to internal validityhistoryregressionmaturationselectiontestingsubject attritionin ...
Ethnobotany and Ethnopharmacology:
Ethnobotany in herbal drug evaluation,
Impact of Ethnobotany in traditional medicine,
New development in herbals,
Bio-prospecting tools for drug discovery,
Role of Ethnopharmacology in drug evaluation,
Reverse Pharmacology.
Unit 8 - Information and Communication Technology (Paper I).pdfThiyagu K
This slides describes the basic concepts of ICT, basics of Email, Emerging Technology and Digital Initiatives in Education. This presentations aligns with the UGC Paper I syllabus.
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This is a presentation by Dada Robert in a Your Skill Boost masterclass organised by the Excellence Foundation for South Sudan (EFSS) on Saturday, the 25th and Sunday, the 26th of May 2024.
He discussed the concept of quality improvement, emphasizing its applicability to various aspects of life, including personal, project, and program improvements. He defined quality as doing the right thing at the right time in the right way to achieve the best possible results and discussed the concept of the "gap" between what we know and what we do, and how this gap represents the areas we need to improve. He explained the scientific approach to quality improvement, which involves systematic performance analysis, testing and learning, and implementing change ideas. He also highlighted the importance of client focus and a team approach to quality improvement.
1. Lecture Outline
Introduction to experimental research
Introduction to correlational research
Three types of research validity
Class Activity
2. Experimental Research
Overview and Major Features
An independent variable (IV) is manipulated
A dependent variable(s) (DV) is measured
Many basic experiments consist of two levels of the independent
variable
experimental group
control group
Control over extraneous variables
holding constant
randomizing effects
A causal relationship between the independent and dependent
variables can be established
3. Basic Goal of Experimental Design
Manipulate possible values of the IV
Observe behavioral changes as indexed by values of the
DV
4. Basic Characteristics of Experimental Designs
Subjects are randomly assigned to research groups
A given participant must be equally likely to be assigned to any of the
given groups
Random number table
Flip a coin
In experimental designs, a causal relationship between the
independent and dependent variables can be established
5. Independent Variable
Differing values of the IV are called “levels”
May vary quantitatively
10 mg day
20 mg day
e.g. here are 2 levels of variable dosage
May vary qualitatively
Zoloft
Imipramine
Prozac
e.g. here are 3 levels of the variable medication type
6. •An operational definition is a clearly defined set of
procedures for measuring or manipulating the construct of
interest.
•The key to an acceptable operational definition is that the
procedure is specified precisely enough to allow replication by
others.
Examples:
quality of memory -- accuracy of recall in a certain task
depression -- Beck Depression Inventory (survey) score
arousal -- galvanic skin response (conductivity of the surface
of the skin)
Operational Definitions
7. She is a good car
salesperson
She:
1. Sells many cars
2. Points out + features
3. Is nice
4. Sells only good cars
Verbal Statement Operational Definition
Operational Definitions: Examples
8. Stress
1. Environment/Number of stressors
a. Number negative Life events
b. Number of Examinations
2. Self-report
Measurable Nervous mood
3. Behavior
a. number of fidgets/minute
b. Psychophysiological
responses elevated
Verbal Statement Operational Definition
Operational Definitions: Examples
9. Identify Key Experimental Features
Social loafing refers to people’s tendency to slack on group tasks.
In one study on social loafing college participants cheered alone,
and in groups of 2, 4, or 6 ppl. They were told to cheer as loud
as possible at specific times so researchers could determine how
much noise people made in social settings. The amount of noise
made by each participant dropped as group size increased.
1) What is the IV?
2) What is the DV?
3) Why is random assignment important here?
10. Correlational Research: Major Features
No independent variables are manipulated
Two or more variables are measured and a relationship established
Correlational research does not show causality
Don’t confuse statistics with research design
Correlation coefficients ( a statistic) can be used in correlational or experimental
research designs (although they are more commonly used in correlational designs)
12. Example of Non-Linear Relationship
Yerkes-Dodson Law
Performance
Arousal
Better
Worse
Low
High
13. Correlation Does Not Imply Causation
Causality – must demonstrate that changes in one
variable can only be due to influence of the other
variable
Directionality of Effect Problem
Third Variable Problem
16. X Y
X Y
Aggressive Behavior Viewing Violent TV
Aggressive Behavior Viewing Violent TV
Aggressive children may prefer violent programs or
Violent programs may promote aggressive behavior
Directionality of Effect Problem
22. Measurement Considerations
Variables should be measured accurately and consistently.
Accuracy
Validity
Bathroom scale gives correct weight
Consistency
Reliability
Bathroom scale gives same weight consistently
23. Evaluating Research: 3 Validities
Validity
How accurate is the information from our research?
Three validities
Construct validity
Internal validity
External validity
25. Construct Validity
The degree to which the construct can be inferred from the operational
definition of that construct
Never one perfect operationalization
Schacter and Singer (1962)
Two-factor theory of emotion:
Emotions require arousal and label
Factor 1: AROUSAL
Participants received epinephrine shots and either
informed them of side-effects or not
Factor 2: LABEL
Participants around "euphoric" or "angry“
confederate
26. How Valid are These Manipulations?
Euphoria
Confederate shoots rubber bands, plays with hula hoops and crumples up
paper and practices hook shots into wastebasket
Anger
Confederate complains about the injection, adds negative comments
about the questionnaire they are filing out and ends up ripping up the
questionnaire.
28. Internal and External Validity
Internal validity
The extent to which the observed effect is caused only by the
experimental treatment condition
The ability to draw conclusions about a causal relationship from our data
Experiments usually high in this
External validity
The extent to which the results can be applied to and across different
persons, settings and times
AKA generalizability
Experiments often low in this
29. Generalizing From the Lab Setting
Mundane realism
The extent to which an experiment is similar to real-life situations
Psychological realism
The extent to which an experiment triggers relevant psychological and
group processes
Key point
Lab experiments not automatically artificial
When an experiment lacks mundane realism it may be very realistic in
terms of psychological realism
30. Assess Internal & External Validity
Does lighting affect productivity?
Study 1:
Give people a production task in a laboratory. The
lab room is either bright or dim. Measure and
compare their productivity (how quickly and
accurately they perform the task).
Study 2:
Give employees in a well-lit office and those in a dim
office a production task. Measure and compare their
productivity (how quickly and accurately they
perform the task).
31. The Tradeoff
Real life situations
High external validity
Hard to rule out other explanations
Low internal validity
Lab settings
High internal validity
Often artificial and findings can’t be generalized
Low external validity