CausalComparative and Experimental Studies

1
Causal-Comparative andExperimental Studies

• Dr. Barrick
• ED 250

2
Definition of Causal-Comparative

• Research that attempts to determine the cause or
  reason for pre-existing differences in groups or
  individuals
• Ex Post Facto Study Study after the fact.
• ExampleHaving your father/mother tutor in math
  at home may be a factor in higher achievement.

3
Purpose of Causal-Comparative Research

• Attempts to identify a cause-effect relationship
  between variables correlational studies do not.
• Causal-Comparative research involves comparison
  not relationship.
• Individual students are not randomly assigned as
  in experimental studies.
• There is no treatment as experimental studies.

4
Examples of Independent Variables in
Causal-Comparative Studies

• Orgasmic Variables
• Age
• Sex
• Ethnicity
• Ability Variables
• Intelligence
• Scholastic Aptitude
• Specific Aptitude
• Perceptual Aptitude

5
More Variables

• Personality
• Anxiety
• Introversion
• Aggression
• Self-concept
• Self-esteem
• Aspiration
• Learning styles

• Family
• Income
• SES status
• Employment status
• Marital status
• Environment
• Birth order
• Number of siblings

6
More Variables

• School
• Preschool attendance
• Size of school
• Type of school
• Per pupil expenditure
• Type of curriculum
• Leadership style
• Teaching style
• Peer pressure

7
Notes

• Definition and selection of comparison groups is
  very important. Selection bias is a danger.
• Lack of randomization, manipulation, and control
  are all sources of weakness.
• There may be another variable which is the real
  cause of the observed difference between groups.

8
Ways to control

• Matching
• Homogeneous groups
• Analysis of covariance

9
Experimental Studies

• Dr. Stan Barrick
• ED 250
• Educational Research

10
Definition of Experimental

• In an experimental study, the researcher
  manipulates at least one independent variable,
  controls other relevant variables, and observes
  the effect on one or more of the dependent
  variables.
• Independent variable is called the experimental
  variable.

11
Steps in Experimental Study

• Selection and definition of the problem.
• Selection of the sample.
• Selection of the instruments.
• Selection of design.
• Execution of procedures.
• Analysis of data.
• Formulation of conclusions.

12
Properties of Experimental Studies

• Has at least one hypothesis that states an
  expected causal relationship between two
  treatment variables.
• Randomly selects the samples for the two or more
  treatments.
• Controls for external variables.
• Has a control group and manipulates a variable.
• Looks for significant differences due to the
  treatment.

13
Experimental Validity

• Any uncontrolled extraneous variables that
  affect performance on the dependent variable are
  threats to the validity of an experiment.
• Internal validity ensuring that the observed
  differences of the dependent variable are due to
  the independent variable.
• External validity ensuring that the results are
  generalizable.

14
Threats to Internal Validity

• History
• Maturation
• Testing
• Instrumentation
• Statistical regression
• Differential selection of sample
• Mortality
• Selection-maturation interaction.

15
History

• The occurrence of events that affect the outcome
  but are not part of the design.
• The longer the experiment lasts the more likely
  that history will interfere.

16
Maturation

• The natural physical, intellectual, and emotional
  changes that occur in the participants over a
  period of time and which affect the dependent
  variable.
• Most likely to be a threat during the
  developmental stages of growth.

17
Testing

• Improved scores on a post-test as a result of
  taking the pre-test.
• Usually a threat when factual information is to
  be recalled.

18
Instrumentation

• The lack of reliability and consistency in the
  measuring instruments.
• Forms of pre-test and post-test are not the same.
• Observations are not normed between observers.
• Mechanical devices which collect data are not
  reliable.

19
Statistical Regression

• Statistical regression occurs when a participant
  scores extremely high or low. On successive
  score will tend toward the mean.
• Can occur when testing gifted or LH students on a
  standardized test.

20
Differential Selection

• Usually occurs when preformed groups are
  compared.
• Example- comparing the students at a community
  college with the students at a university.

21
Mortality

• Attrition of participants affects the study.
• Example- the study of a teaching method with one
  group having a high mobility rate.

22
Selection Interactions

• Selection interacts with maturation.
• Selection interacts with history.
• Selection interacts with instrumentation.
• Etc.

23
Threats to External Validity

• Pre-test treatment interaction.
• Selection treatment interaction.
• Multiple treatment interaction.
• Specificity of variables.
• Treatment diffusion.
• Experimenter effect. Pygmilan Effect
• Reactive effect. Hawthorne Effect

24
Pre-Experimental Designs

• One shot case X O
• One group pre/post-test 0 X O
• Static group comparison

25
Experimental Designs

• Pre/Post test control group
• Post test only control group

26
Experimental Designs

• Solomon four group design

27
Quasi-Experimental Designs

• Non-equivalent control group
• Time Series

28
Quasi-Experimental

• Counterbalanced