Post on 30-Dec-2015
Experimental Designs-random assignment
• pretest data cannot be collected
• postest only design
• pretest data can be collected
• pretest-postest design
QUASIEXPERIMENTAL DESIGNno random assignment to groups
• pretest data cannot be collected
• postest only design
• pretest data can be collected
• pretest-postest design
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 Designs
O=measurement of dep. variable
X=application of indep. variable
R=randomization
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
• lack either randomization and or a control group.
(always have manipulation)
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
• -less confidence in causality
• -need a priori controls
• -must rule out alternative explanations
• -need more replication
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
• collect detailed data on the status quo
• determine differences between varibles
Descriptive Surveys
• Use: questionnaires or interviews
• Large samples
• Superficial information emphasizes breadth rather than depth.
• Researcher needs knowledge of techniques.
• Can be costly.
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
Disadvantages:
the researcher is unable to manipulate the variables
generalizability is decreased (preexisting groups)
no causal relationship
disadvantages:
• no causality
• must rule out alternative explanations
• finding similar comparison groups difficult
Methodological Research
• Instrument Construction and Testing
(psychometrics)
• Perfecting Research Techniques