Experimental Designs for Research in Education
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Identify a treatment variable
Identify the conditions (or levels) of the variable
Manipulate the treatment conditions
MANIPULATING
TREATMENT CONDITIONS
1.
Experimental
Designs
-this is the independent variable
2.
-these are the levels of the independent variable
3.
-do something different for each condition
RANDOM ASSIGNMENT
GROUP COMPARISONS
Process of a researcher obtaining scores for individuals or groups on the dependent variable and comparing the means and variance both within the group and between the groups
The process of assigning individuals at random to groups or to different groups in an experiment
Equating the groups
Spelling Accuracy
Random assignment equates groups and distributes variability between or among groups and conditions
Phase 1: Relationship Picture
Test 1 Test 2 Test 3
6 weeks 6 weeks 6 weeks
6 weeks 6 weeks 6 weeks
6 weeks 6 weeks 6 weeks
Phase 2: Timeline Picture
Phase 3: Statistical Comparisons
Error Correction Treatment
Random selection
Randomly selecting a sample from a population
Class A (control group)
Class B
(comparison group)
Class C
(experimental group)
Experimental
Designs
THREATS TO VALIDITY
What is it?
How does it work?
When do we use it?
CONTROL OVER EXTRANEOUS VARIABLES
EXPERIMENTAL DESIGN PROCESS
In an experiment you test an idea to determine whether it influences an outcome or dependent variable
Maturation
We use experiments when we want to establish possible cause and effect between independent and dependent variables
1.
Determine if an experiment is the appropriate research approach for your study
Instrumentation
or
2.
Determine activities with which to “experiment”
History
Testing
when we have two or more groups to study
3.
Assign individuals to experience the experiment (and have some individuals experience something different)
Resentful demoralization
External
Influences in the selection of participants, the procedures, the statistics, or the design likely to affect the outcome and provide an alternative explanation for our results than what was expected
4.
Determine whether those who experienced the activities (or practice or procedure) performed better on some outcome than those who did not experience the same thing
Selection
Regression
The degree to which the findings are generalizable to a population
Internal
Interaction of selection and treatment
Interaction of history and treatment
MATCHING BASED ON GENDER
Interaction of setting and treatment
INTERVENTION
This is a variable the researcher controls before the experiment starts by dividing (or "blocking") the participants into subgroups (or categories) and analyzing the impact of each subgroup on the outcome
Mortality
Problems that threaten our ability to draw correct cause-and-effect inferences that arise because of our procedures or participant experiences
The researcher forms homogeneous subgroups
POSTTEST
1.
This is the process of identifying one or more personal characteristics that influence the outcome and assigning individuals with that characteristic equally to the experimental and control groups
Then the investigator randomly assigns individuals to the control and experimental groups using each category of the variable
2.
PRETEST
Interaction with selection
Matching of Participants
Blocking Variables
Pretests and Posttests
Compensatory rivalry
Compensatory equalization
Diffusion of treatments
No Covariate
Dependent Variable
Independent Variable
This is the process of selecting people who vary little in their personal characteristics
Dependent Variable
GPA
Gender
Age
Similar:
Independent Variable
Racial Group
Degree Program
Covariate Introduced
Covariate
Thus, these characteristics or attributes are controlled in the experiment
Covariates
Homogeneous Samples
Variables that the researcher controls for using statistics and that relate to the dependent variable but that do not relate to the independent variable
EDFI 6420
Research in Education
Amanda Kochmit
Matt Priest
Lindsay Whitman Drewes
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