What do you call it when both the researcher and participants are ignorant about whether the participants have received the treatment or a placebo?
To make things easier, the following will act as representations within particular designs:
The three experimental designs discussed in this section are: Show The One Shot Case StudyThis is a single group studied only once. A group is introduced to a treatment or condition and then observed for changes which are attributed to the treatmentX O The Problems with this design are:
One Group Pre-Posttest DesignThis is a presentation of a pretest, followed by a treatment, and then a posttest where the difference between O1 and O2 is explained by X:O1 X O2 However, there exists threats to the validity of the above assertion:
The Static Group ComparisonThis is a two group design, where one group is exposed to a treatment and the results are tested while a control group is not exposed to the treatment and similarly tested in order to compare the effects of treatment.Threats to validity include:
The next three designs discussed are the most strongly recommended designs: The Pretest-Posttest Control Group DesignThis designs takes on this form:This design controls for all of the seven threats to validity described in detail so far. An explanation of how this design controls for these threats is below.
The factors described so far effect internal validity. These factors could produce changes which may be interpreted as the result of the treatment. These are called main effects which have been controlled in this design giving it internal validity. However, in this design, there are threats to external validity (also called interaction effects because they involve the treatment and some other variable the interaction of which cause the threat to validity). It is important to note here that external validity or generalizability always turns out to involve extrapolation into a realm not represented in one's sample. In contrast, internal validity are solvable within the limits of the logic of probability statistics. This means that we can control for internal validity based on probability statistics within the experiment conducted, however, external validity or generalizability can not logically occur because we can't logically extrapolate to different conditions. (Hume's truism that induction or generalization is never fully justified logically). External threats include:
Research should be conducted in schools in this manner--ideas for research should originate with teachers or other school personnel. The designs for this research should be worked out with someone expert at research methodology, and the research itself carried out by those who came up with the research idea. Results should be analyzed by the expert, and then the final interpretation delivered by an intermediary. Tests of significance for this design--although this design may be developed and conducted appropriately, statistical tests of significance are not always used appropriately.
The Soloman Four-Group DesignThe design is as:
In this design, subjects are randomly assigned to four different groups: experimental with both pre-posttests, experimental with no pretest, control with pre-posttests, and control without pretests. By using experimental and control groups with and without pretests, both the main effects of testing and the interaction of testing and the treatment are controlled. Therefore generalizability increases and the effect of X is replicated in four different ways. Statistical tests for this design--a good way to test the results is to rule out the pretest as a "treatment" and treat the posttest scores with a 2X2 analysis of variance design-pretested against unpretested. The Posttest-Only Control Group DesignThis design is as: This design can be though of as the last two groups in the Solomon 4-group design. And can be seen as controlling for testing as main effect and interaction, but unlike this design, it doesn't measure them. But the measurement of these effects isn't necessary to the central question of whether of not X did have an effect. This design is appropriate for times when pretests are not acceptable.Statistical tests for this design--the most simple form would be the t-test. However covariance analysis and blocking on subject variables (prior grades, test scores, etc.) can be used which increase the power of the significance test similarly to what is provided by a pretest. As illustrated above, Cook and Campbell devoted much efforts to avoid/reduce the threats against internal valdity (cause and effect) and external validity (generalization). However, some widespread concepts may also contribute other types of threats against internal and external validity. Some researchers downplay the importance of causal inference and assert the worth of understanding. This understanding includes "what," "how," and "why." However, is "why" considered a "cause and effect" relationship? If a question "why X happens" is asked and the answer is "Y happens," does it imply that "Y causes X"? If X and Y are correlated only, it does not address the question "why." Replacing "cause and effect" with "understanding" makes the conclusion confusing and misdirect researchers away from the issue of "internal validity." Some researchers apply a phenomenological approach to "explanation." In this view, an explanation is applied to only a particular case in a particular time and place, and thus generalization is considered inappropriate. In fact, a particular explanation does not explain anything. For example, if one askes, "Why Alex Yu behaves in that way," the asnwer could be "because he is Alex Yu. He is a unqiue human being. He has a particular family background and a specific social circle." These "particular" statements are alway right, thereby misguide researchers away from the issue of external validity. What is it called when participants don't know they are being observed?Researchers engaged in naturalistic observation usually make their observations as unobtrusively as possible so that participants are not aware that they are being studied. Such an approach is called disguised naturalistic observation .
What type of bias is the placebo effect?Patients receiving placebo, and believing they are receiving (or have a fair chance of receiving) genuine treatment are less likely to seek alternative treatment, or to modify their basic care treatment, so-called co-intervention bias.
What is the term for when neither the researcher nor the participant is aware of what group they are assigned to?Listen to pronunciation. (DUH-bul-blind STUH-dee) A type of clinical trial in which neither the participants nor the researcher knows which treatment or intervention participants are receiving until the clinical trial is over.
Which participants in a study do not receive the treatment?A control group consists of participants who do not receive any experimental treatment. The control participants serve as a comparison group. The control group is matched as closely as possible to the experimental group, including age, gender, social class, ethnicity etc.
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