This is a draft cheat sheet. It is a work in progress and is not finished yet.
Key Terms
Response variable: variable that measures an outcome or result of study. |
Explanatory variable: variable that we think explains or causes changes in the response variable. |
Individuals studied in an experiment are often called subjects |
A treatment is any specific experimental condition applied to the subjects. If an experiment has several explanatory variables, a treatment is a combination of specific values for these variables. |
Lurking Variable: variable that has an important effect on the relationship among the variables in the study but is not one of the explanatory variables studied |
Two variables are confounded when their effects on a response variable cannot be distinguished from each other. |
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the confounded variables may be either explanatory or lurking variables. |
Chapter 6 Key Terms
double blind experiment: neither the subject nor the people who work with them know which treatment the subject is receiving |
clinical trials: medical experiments involving human subjects. |
nonadherers: subjects who participate but don't follow experimental treatment |
experiments that continue over an extended period of time also suffer dropouts: subjects to begin the experiment but do not complete it. |
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If a subject drops out because of their reaction to one of the treatments, bias can occur. |
a well designed experiment tells us that changes in the explanatory variable must cause changes in the response variable. |
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make sure that your findings are statistically significant, that they are too strong to occur by chance. |
Completely Randomized Design (experimental design): all the experimental subjects are allocated at random among all the treatments. |
Matched Pairs Design (matching and randomization): compares just two treatments |
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choose a pair of subjects that are as closely matched as possible. Assign one of the treatments to each subject by random assignment. |
Block design: group of experimental subjects that are known before an experiment to be similar in some way that is expected to affect the response of the treatments |
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random assignment of subjects to treatments is carried out separately within each block. |
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combines the idea of creating equivalent treatment groups. |
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another form of control. Some outside variables are controlled by bringing those variables into the experiment to form the blocks. |
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Chapter 5
placebo effect: dummy treatment with no active ingredients. |
Randomized Comparative Experiment: one that compares two treatments. |
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random assignment into groups, one group for each treatment |
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make sure to include one control group. |
Chapter 7
The organization that carries out the study must have an institutional review board that reviews all planned studies in advance in order to protect the subjects from possible harm. |
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purpose:to protect the rights and welfare of human subjects recruited to participate in research activities. |
All individuals who are subjects in a study must give their informed consent before data is collected. |
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must be informed about the nature of the study and risk. |
All individual data must be kept confidential. Only statistical summaries for groups of subjects may be made public. |
Anonymity: subjects are anonymous - their names are not known even to the director of the study. |
Confidentiality: |
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Logic of Experimental Design
Randomization produces group of subjects that should be similar in all respects before we apply the treatments. |
Comparative design ensures that influences other than the experimental treatments operate equally on all groups. |
Therefore, differences in the response variable must be due to the effects of treatments |
Principles of Experimental Design |
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1. Control. The effects of lurking variables on the response, most simply by comparing two or more treatments |
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2. Randomize. Use impersonal chance to assign subjects to treatments. |
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3. Use enough subjects in each group to reduce chance variation in the results. |
Statistical Significance: an observed effect of a size that would rarely occur by chance |
Good studies are comparative even when they are not experiments. |
We can often combine comparison with matching in creating a control group |
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note: matching does not entirely eliminate confounding |
A good comparative study measures and adjusts for confounding variables. |
Clinical Trials
Clinical Trials: experiments that study the effectiveness of medical treatments on actual patients. |
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Randomized comparative experiments are the only way to see the true effects of these new treatments. Without them, risky treatments that are no better than placebos will become common |
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Clinical trials produce great benefits, but most of these go to future patients. The trials pose risks which are borne by the subjects. Balance future benefits against risks |
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Both medical ethics and international human rights standards say that |
Clinical Trials
Clinical Trials: experiments that study the effectiveness of medical treatments on actual patients. |
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Randomized comparative experiments are the only way to see the true effects of these new treatments. Without them, risky treatments that are no better than placebos will become common |
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Clinical trials produce great benefits, but most of these go to future patients. The trials pose risks which are borne by the subjects. Balance future benefits against risks |
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Both medical ethics and international human rights standards say that the interest of the subject must always prevail over the interests of science and society. |
Behavioral and Social Science experiments |
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the direct risks to experimental subjects are less acute, but so are the possible benefits. |
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invasion of privacy, informed consent are both issues in these studies |
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