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Quantitative Research
SPED 500
Dr. Sandra Beyda
• Designs that maximize objectivity by using numbers, statistics, structure, and experimenter control
• Modes– Experimental mode– Non-experimental
mode
Structure of a Data Based Study
• Abstract• Introduction• Method• Results• Discussion• Summary & Conclusions• References
True experiment
Quasi-experimental
Single Subject
True Experiments
• Internal validity
• External validity– Randomization– Systematically vary or manipulate– Hold constant– Assume invariance or irrelevance– Matching– Statistical control
Threats to Internal Validity
When there is a statistically significant result (X > Control)
History MaturationTesting
Nonequivalence
Regression
Mortality
Interactions with Selection
Instrumentation
Threats to Internal Validity
When there are non-significantly different results:
Small sample size
Treatment implementation
Insensitive dependent variable
John Henry EffectTreatment not long enough
Treatment diffusion
Threats to External Validity
• Population validity• Ecological validity• Operations validity
• Posttest only • Pretest-Posttest• Solomon 4 Group Design• Factorial Design
• No Random Assignment!
• One group• Time series approach
• Two groups• Static group comparison
• Non-equivalent control group
• Reliable measurements
• Repeated measurements
• Baseline
• Introduction of treatment
• Reversal or withdrawal
• Maintenance• Replication
Single Subject Research Designs
AB
ABAABAB
Multiple Baseline
How about a little practice exercise?
Don’t worry. I’ll wait!
• Descriptive
• Comparative
• Correlational
• Ex Post Facto
Descriptive Research
• Single Group• Cross-sectional• Longitudinal
Comparative Research
Correlational Research
• Purpose: What is the relationship between variable A and B?
• Uses:– Theory building
– Establish predictive relationships
Correlational Research
• Bivariate correlational studies
• Prediction studies– Predictor variable
– Criterion variable
Correlational Research Limitations
• Correlation and Causation
• Spurious Correlations
• Size of Correlation Coefficients
• Purpose: – To examine how an identified independent
variable effects the dependent variable when circumstances do not allow for the manipulation of the independent variable
• Conditions for establishing cause-effect connections – (1) statistical significance-– (2) IV before DV. – (3) Alternative causes
Ex-Post Facto ResearchDesigns
• Single Group• Between Group
• Problems– Self selection
– Correlation-causation fallacy
– Direction of causality