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4 - all the treatments Completely randomized designs can...

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4 Subject: The individuals studied in an experiment are often called subjects, particularly when they are people. The explanatory variables in an experiment are often called factors. A treatment is any specific experimental condition applied to the subjects. If an experiment has more than one factor, a treatment is a combination of specific values of each factor. In an experiment, we can study the effects of the specific treatments we are interested in. By assigning subjects to treatments, we can avoid confounding. Another advantage of experiments is that we can study the combined effects of several factors simultaneously. Uncontrolled experiments often yield worthless results because of confounding with lurking variables. An experiment that uses both comparison of two or more treatments and random assignment of subjects to treatments is a randomized comparative experiment. In a completely randomized experimental design, all the subjects are allocated at random among
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Unformatted text preview: all the treatments. Completely randomized designs can compare any number of treatments. Here is an example that compares three treatments. Replication is the amount of the subjects (individuals) of an experimental condition so that the variability associated with the phenomenon can be estimated. Comparing two active treatments enables the researcher to determine which treatment works best. When we compare two comparison groups both having active treatments and if the difference is statistically significant, we will know which active treatment works best. An experiment can be used to establish causation. Because the researcher imposes a treatment on each individual in the study and measures the response, the researcher can use the results to establish whether the treatments “cause” changes in the response. Randomized comparative experiments: principle 1. Control or comparison 2. Randomization 3. Replication...
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