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Experimental Research. by Dr. Daniel Churchill. Task Presentation. Correlational Research Question. What is Experimental Research. Test hypotheses concerning cause and effect relationships - PowerPoint PPT Presentation
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Methods of Research and Enquiry
Experimental Researchby Dr. Daniel Churchill
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Task Presentation
Correlational Research Question
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What is Experimental Research
Test hypotheses concerning cause and effect relationships
A researcher manipulates at least one independent variable, controls other variables and observes effect on one or more independent variables.
Usually there are different groups of subjects who get different treatment
Individuals randomly assigned to treatment groups
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Experimental research
Most studies compare groups When individuals are studies, the studies
are called single-case (or single subject) designs.
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Experimental Process
Six steps to conducting experimental research Selection and definition of the problem
Statement of a hypothesis indicating a causal relationship between variables
Selection of participants and instruments Random selection of a sample of subjects from a
larger population Random assignment of members of the sample to
each group Selection of valid and reliable instruments
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Experimental Process Six steps to conducting experimental
research (cont.) Selection of a research plan
Three types of comparisons Comparison of two different approaches Comparison of new and existing approaches Comparison of different amounts of a single approach
Execution of the research plan Two concerns
Sufficient exposure to the treatment Substantively different treatments
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Experimental Process
Six steps to conducting experimental research (cont.) Analysis of data Formulation of conclusions
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Manipulation and Control Manipulation
The researcher’s decisions related to what constitutes the independent variable
Active and assigned variables Active variables are those the researcher actively
manipulates Choice of an instructional strategy A particular counseling approach
Assigned variables are those that cannot be manipulated by the researcher but are of interest
Gender Race
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Manipulation and Control
Control The researcher’s efforts to remove the influence of any
extraneous variables that might have an effect on the dependent variable
The goal is to be assured the only differences between groups is that related to the independent variable
Participant variables – characteristics of the subjects Pre-existing achievement levels Differences in attitudes
Environmental variables – characteristics of the context Learning materials Differences in the time available for treatment between groups
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Group Designs
Two major classes of group designs Single-variable designs – one independent
variable Factorial designs – two or more independent
variables
Three types of experimental designs Pre-experimental designs Experimental designs Quasi-experimental designs
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Pre-Experimental Designs
Three types One-shot case study
X O
One-group pretest-posttest design O X O
Static group comparison X1 O
X2 O
Threats to internal validity – see Figure 9.1
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True Experimental Designs
Three types Pretest-posttest control group design
R O X O
R O O
Posttest only control group design R X O
R O
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True Experimental Designs Three types (cont.)
Solomon four-group comparison R O X O
R O O
R X O
R O
Threats to internal validity – see Figure 9.2
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Quasi-Experimental Designs Three types
Non-equivalent control group design O X O
O O
Time series design O O O O X O O O O
Counterbalanced design O X1 O X2 O X3 O
O X3 O X1 O X2 O
O X2 O X3 O X1 O
Threats to internal validity – see Figure 9.2
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Factorial Designs Two independent variables and one dependent
variable The effect of teaching strategy and gender on
students’ achievement The effect of a particular counseling technique and
the clients’ ethnicity on the success of the treatment The effect of a specific coaching approach and
children in three age groups on the ability to perform certain physical tasks
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Factorial Designs Interaction
Visually explained by a graph of performance of all levels of both independent variables Parallel lines indicate no interaction Non-parallel lines indicate an interaction
Statistically examined with an F-test of the statistical significance of the interaction
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Factorial Designs Interaction
Visual presentation of a significant interaction
Statistical analysis of this significant interaction: F1,16 = 4.88 (p = .0420)
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TEST
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Factorial Designs Interaction
Visual presentation of a non-significant interaction
Statistical analysis of this non-significant interaction: F1,16 = 0.97 (p = .340)
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Measurement Scales
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Inferential Statistics
Applied only when groups are compared T-test is used to compare experimental
group to control group, boys to girls, pre-tests to post-tests, etc
The numbers used for comparison are means
Interval or ratio scale derived form the same measure (e.g., same test)
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Hypotheses for t-test
H0 Mean 1= Mean 2
HA Mean 1 Mean 2 T value is calculated using a specific
formula Statistical tables are used to determine
level of significance (check http://www.statsoft.com/textbook/sttable.html)
H0 is kept or rejected (check the table)
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Inferential Statistics
ANOVA is used to compare mean of two or more samples and to test whether the differences are statistically significant.
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Useful reading
Here is a useful reading written by HKU professor
Interesting resource for learning about statistics is available here:http://www.mnstate.edu/wasson/ed602.htm
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Task to be completed before next class
Your group should discuss some possible question that can be classified as Experimental Research. In your blog propose potential experimental research question, how could data for the related variables be collected, and provide argument how answer to that question can contribute to improvements in some aspect of education/teaching and learning.
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References
Gay, L. R., Mills, G. E., & Airasian, P. (2006). Educational Research: Competencies for Analysis and Applications. Upper Saddle River, N.J. : Pearson/Merrill Prentice Hall.
Ravid, R. (2000). Practical statistics for educators. (2nd ed). New York, NY.: University Press of America, Inc.