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RESEARCH DESIGNS. OVERVIEW. EXPERIMENTAL DESIGNS. When the Research Question Deals “with what happens if”. pretest data cannot be collected postest only design. pretest data can be collected pretest-postest design. Experimental Designs-random assignment. pretest data cannot be collected

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experimental designs random assignment
pretest data cannot be collected

postest only design

pretest data can be collected

pretest-postest design

Experimental Designs-random assignment
quasiexperimental design no random assignment to groups
pretest data cannot be collected

postest only design

pretest data can be collected

pretest-postest design

QUASIEXPERIMENTAL DESIGNno random assignment to groups
causality
Causality
  • TEMPORAL SEQUENCE
  • CONCOMITANT VARIATION
  • ABSENCE OF COMPETING EXPLANATIONS
experimentation
EXPERIMENTATION
  • RANDOMIZATION
  • CONTROL
  • MANIPULATION
logic of a true experiment
LOGIC OF A TRUE EXPERIMENT
  • When one starts a study with two groups who are equal with respect to important variables, administers a treatment to one group (experimental group) and not to the other (control group) holding all other conditions constant, any differences in the dependent variable following treatment probably were the result of that treatment.
experimental designs1

Experimental Designs

O=measurement of dep. variable

X=application of indep. variable

R=randomization

solomon four group
Solomon Four group

R O X O

R O O

R X O

R O

repeated measures
Repeated Measures

R OOOO X OOOO

R OOOO OOOO

factorial design
FACTORIAL DESIGN

experimental if random assignment to cell

advantages of experiments
Advantages of Experiments
  • -test cause and effect
  • -control threats to internal validity
disadvantages of experiments
Disadvantages of Experiments
  • -assumes all of the relevant variables have been identified
  • -some variables not manipulable
  • -randomization may pose difficulties in field studies
  • -Hawthorne effect may not be avoidable
quasiexperimental designs
quasiexperimental designs
  • lack either randomization and or a control group.

(always have manipulation)

crossover design
Crossover design

OO X OO X OO OO

advantages of quasi experiments
Advantages of Quasi-Experiments
  • -practical, feasible,generalizable
  • -adaptable to field studies
  • -for some hypotheses they may be the only way to test
  • -may save some experiments that suffer from attrition
disadvantages
Disadvantages
  • -less confidence in causality
  • -need a priori controls
  • -must rule out alternative explanations
  • -need more replication
objectives
objectives:
  • --to discover whether and how well objectives are being fulfilled
  • --to discover the reasons for specific successes and failures
  • --to direct the cours of experiment with techniques for increasing effectiveness
  • --to uncover principles underlying a successful program
  • --to redefine goals and objectives and means of obtaining them
descriptive exploratory survey
DESCRIPTIVE/EXPLORATORY SURVEY
  • collect detailed data on the status quo
  • determine differences between varibles
descriptive survey research
Descriptive/Survey Research
  • CHARACTERISTICS
  • ATTITUDES
  • FACTS
  • OPINIONS
  • BELIEFS
  • BEHAVIORS
descriptive surveys
Descriptive Surveys
  • Use: questionnaires or interviews
  • Large samples
  • Superficial information emphasizes breadth rather than depth.
  • Researcher needs knowledge of techniques.
  • Can be costly.
descriptive correlational studies
Descriptive Correlational Studies
  • Tests covariance between variables
advantages
advantages
  • increased flexibility when investigating complex relationships among variables
  • efficient and effective method of collecting a large amount of data about a problem
  • potential for practical application in clinical settings
  • foundation for future experimental research studies
  • explores relationships between variables that are inherently not manipulable
disadvantages1
Disadvantages:
  • the researcher is unable to manipulate the variables
  • generalizability is decreased (preexisting groups)
  • no causal relationship
ex post facto designs
EX POST FACTO DESIGNS

“natural experiment”

  • independent variable not manipulated
types of ex post facto studies
Types of Ex Post Facto Studies

prospective retrospective

longitudinal cross-sectional

advantages1
advantages:
  • similar to correlational advantages
  • realistic and natural
disadvantages2
disadvantages:
  • no causality
  • must rule out alternative explanations
  • finding similar comparison groups difficult
methodological research
Methodological Research
  • Instrument Construction and Testing

(psychometrics)

  • Perfecting Research Techniques