A fitness instructor wants to test the effectiveness of a performance-enhancing herbal supplement on students in her Pilates exercise class. She randomly assigns students into two groups. The instructor gives Group 1 the herbal supplement and Group 2 receives a placebo. The fitness level of each student is compared before beginning the treatment and again after six weeks of consuming the supplement or placebo. Does this describe an observational research study or an experimental research study? Experimental Research Study Observational Research Study
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An **observational study** involves observing subjects and measuring variables of interest without assigning treatments to the subjects. The researcher does not intervene or manipulate any variables. An **experimental study** involves applying a treatment to a Show more…
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A study was conducted to evaluate the impact of taking a nutritional supplement on a person's reaction time. One hundred volunteers were placed into one of three groups according to their athletic ability: low, moderate, or high. Participants in each group were randomly assigned to take either the nutritional supplement or a placebo for six weeks. At the end of the six weeks, participants were given a coordination task. The reaction time in completing the task was recorded for each participant. The study compared the reaction times between those taking the supplement and those taking the placebo within each athletic ability level. Which of the following is the best description of the study? (A) A randomized block design (B) A completely randomized design (C) A matched-pairs design (D) A randomized observational study (E) A stratified observational study
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