1. An experiment was carried out to investigate the e§ect of di§erent treatments
ID: 3302948 • Letter: 1
Question
1. An experiment was carried out to investigate the e§ect of di§erent treatments on pain relief for migraine su§erers. 120 migraine su§erers were randomly allocated to three groups where one group took medication, one group changed their diet and one group received a placebo. After a month, each subject classiÖed their pain relief into two categories ñno pain relief and some pain relief.
(a) Why is this study classiÖed as an experiment?
(b) What are the response variable and the explanatory variable in this experiment?
(c) What is the type and scale of measurement of the response variable data?
Explanation / Answer
(a) This study is classified as an experiment because in an experiment investigators apply treatments to experimental units/subjects and then proceed to observe the effect of the treatments on the experimental units. Here the experimental units are the migraine sufferers and the treatments are the medication, changed their diet and placebo. Since the sujects are randomly allotted to the treatments this is random experiment.
(b)
The response variable is the pain relief which is considered as two categories no pain relief and some pain relief.
The explanatory variables are the treatments: medication, changed their diet and placebo.
(c)
The response variable is a categorical variable as the degree of relief in pain is not measurable. So we can only classify it as pain relief or some pain relief. It is thus a nominal variable with only 2 categories(here no pain relief and some pain relief). Such a variable is also called as a “dichotomous” variable.
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