- Quasi-experimental design
A quasi-experiment is a scientific research method primarily used in the
social sciences. “Quasi” means likeness or resembling, so therefore quasi-experiments share characteristics of true experimentswhich seek interventions or treatments. The key difference in this empiricalapproach is the lack of random assignment. Another unique element often involved in this experimentation method is use of time series analysis: interrupted and non-interrupted.
The first part of creating a quasi-experimental design is to identify the variables. The
quasi-independent variablewill be the x-variable. This is the variable that is manipulated in order to affect the outcome. “X” is generally a grouping variablewith different levels. Grouping means two or more groups such as a treatment group and a placebogroup. The predicted outcome is the dependent variablewhich is the y-variable. In a time series analysis, the dependent variable is observed over time for any changes that may take place. Once the variables have been identified and defined, a procedure should then be implemented and group differences should be examined. [ [http://pareonline.net/getvn.asp?v=5&n=14 True and quasi-experimental designs. Gribbons, Barry & Herman, Joan ] ]
Since quasi-experimental designs are used when
randomizationis impossible and/or impractical, they are typically easier to set up than true experimental designs; [ [http://www.otal.umd.edu/hci-rm/cntlexp.html CHARM-Controlled Experiments ] ] it takes much less effort to study and compare subjects or groups of subjects that are already naturally organized than to have to conduct random assignmentof subjects. Additionally, utilizing quasi-experimental designs minimizes threats to external validity. [http://www.osulb.edu/~msaintg/ppa696/696quasi.htm] Since quasi-experiments are natural experiments, findings in one may be applied to other subjects and settings, allowing for some generalizationsto be made about population. Also, this experimentation method is efficient in longitudinalresearch that involves longer time periods which can be followed up in different environments.
The control allowed through the manipulation of the x-variable can lead to unnatural circumstances. Also, the lack of random assignment in the quasi-experimental design method may allow studies to be more feasible, but this also poses many challenges for the investigator. This deficient in randomization makes it harder to rule out
confoundsand introduces new threats to internal validity. [http://www.monash.edu.au/muarc/safebk/Chp_4.pdf] Because randomization is absent, some knowledge about the data can be approximated, but cause-effectconclusions are difficult to determine. Moreover, even if these threats to internal validity are assessed, causationstill cannot be fully established because the experimenter does not have total control over variables. [ [http://linguistics.byu.edu/faculty/henrichsenl/ResearchMethods/RM_2_09.html Research Methods: Planning: Quasi-Exper. Designs ] ]
Wikimedia Foundation. 2010.
См. также в других словарях:
Bayesian experimental design — provides a general probability theoretical framework from which other theories on experimental design can be derived. It is based on Bayesian inference to interpret the observations/data acquired during the experiment. This allows accounting for… … Wikipedia
Design of quasi-experiments — The design of a quasi experiment relates to a particular type of experiment or other study in which one has little or no control over the allocation of the treatments or other factors being studied. The key difference in this empirical approach… … Wikipedia
Design of experiments — In general usage, design of experiments (DOE) or experimental design is the design of any information gathering exercises where variation is present, whether under the full control of the experimenter or not. However, in statistics, these terms… … Wikipedia
Experimental data — Data produced by an experimental or quasi experimental design. In clinical research any data produced as a result of clinical trial.Experimental data may be qualitative or quantitative, each being appropriate for different investigations.… … Wikipedia
Design-based research — (DBR) is a type of research methodology commonly used by researchers in the Learning Sciences. Within Design Based Research methodology, interventions are conceptualized and then implemented in natural settings in order to test the ecological… … Wikipedia
Experimental techniques — Experimental research designs are used for the controlled testing of causal processes. The general procedure is one or more independent variables are manipulated to determine their effect on a dependent variable. These designs can be used where:… … Wikipedia
Quasi Universal Intergalactic Denomination — The Quasi Universal Intergalactic Denomination, called the Quid , is a prototype for a possible future type of currency for use by space tourists.Cite web|url=http://news.bbc.co.uk/1/hi/business/7029564.stm|title=New currency for space… … Wikipedia
Multiple baseline design — A multiple baseline design is a style of research involving the careful measurement of multiple persons, traits or settings both before and after a treatment. This design is used in medical, psychological and biological research to name a few… … Wikipedia
Ex-post-facto-Design — Das Forschungsdesign (auch Untersuchungsdesign, Untersuchungs oder Versuchsanordnung, Versuchsplan) ist die Grundlage jeder wissenschaftlichen Untersuchung. Es beschreibt, wie die empirische Fragestellung untersucht werden soll. Es beinhaltet die … Deutsch Wikipedia
Ex-post-facto Design — Das Forschungsdesign (auch Untersuchungsdesign, Untersuchungs oder Versuchsanordnung, Versuchsplan) ist die Grundlage jeder wissenschaftlichen Untersuchung. Es beschreibt, wie die empirische Fragestellung untersucht werden soll. Es beinhaltet die … Deutsch Wikipedia