1. A researcher conducts a study to determine if moderate exercise (weekly speed
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1. A researcher conducts a study to determine if moderate exercise (weekly speed walking) is effective for treating depression. The researcher recruited ten volunteers with clinical depression by posting advertisements near the university food court. None of the participants were taking anti-depressants, but some were in therapy. The exercise treatment involves a daily 30-minute brisk walk. The participants take a mood survey prior to the start of the study, and then every three months until the end of the study. The study lasted one year. Interestingly all participants reported either improvements or worsening of mood over time. During the study, three participants dropped out of the study.
What kind of sampling was conducted for the study?
Convenience sampling
Quota sampling
Simple random sampling
Stratified random sampling
In order to account for participant attrition, what must be done before the study begins?
Name the research design used to determine the effect of exercise
Between-group Within-group
Name one advantage of using this research design to determine the effect of exercise?
What role did mood play in this experiment?
Confounding variable Obscuring variable
2. A researcher observed children with and without ADHD as they are playing with a jigsaw puzzle. The following table reports the amount of time (in minutes) that each child engaged with the puzzle: TIME WITH PUZZLE(MIN)
The difference between these two groups of children is about 5 minutes and the standard deviation is 3.7 minutes. How many children would the researcher need in each group to reach a statistically significant difference? (Hint: use the power equation)
Did the researcher observe enough children in each of these groups?
Yes No
The difference between these two groups of children is about 5 minutes. What does the difference reflect:
Between-group variability Within-group variability
The time that children without ADHD interacted with the puzzle ranged between 11-18 min. What does this range in responses reflect?
Between-group variability Within-group variability
3. A recent study showed that vitamin D supplementation in multiple sclerosis patients have a decreased relapse incidence rate. The researchers measured the relapse incidence rate for six months before vitamin D supplementation and six months after the vitamin D supplementation on several occasions. The participants in this study were all volunteers who were associated with the medical clinic.
Which of the following research strategies would this study fall under?
Non-experimental
Quasi-experimental
Experimental
What kind of research design was this study?
Posttest-only non-equivalent control group study
Pretest-posttest non-equivalent control group design
Time series design
Longitudinal design
What is the pre-existing independent variable that is being studied?
4. A researcher is writing a research protocol to study the effects of a new drug, Drug N, on food intake in rats. The researcher wants to determine the optimal dose and established three independent groups, which received either 0 mg/ml; 5 mg/ml; or 10 mg/ml of Drug N. Food consumed is determined 3 hours after the rats were given an intraperitoneal injection of Drug N.
What is the minimum total number of rats the researcher should start with?
What research design was used in this study?
Between-group Within-group
The researcher suggests that Drug N can be used as an appetite stimulant in patients who are terminally ill or have eating disorders. Which of the following limits the conclusions the researcher makes about Drug N?
Cross-species generalization
Timing of measurement
Pre-existing differences in humans
Explanation / Answer
We are allowed to do 1 question at a time. Post again for second question.
1) a) A convenience sample is a non-probability sample in which the researcher uses the subjects that are nearest and available to participate in the research study. This technique is also referred to as "accidental sampling," and is commonly used in pilot studies prior to launching a larger research project.
b) Attrition is a concern for within subjects designs, as they require more commitment from the participant. Surveys, research projects and other data collection methodologies often have a margin of error built in to address factors beyond a researcher’s control. For example, a researcher may claim a study has a potential error rate of plus or minus a certain percentage that is factored based on participant attrition. This helps reviewers and users of the data understand the variables on which the researcher is basing any suppositions. Authors could consider presenting a table showing baseline characteristics of those who were and were not analysed when reporting secondary outcomes. The table might look different for different analyses of the same study. Although this table would require increased journal space, the information is arguably more useful than that in a standard baseline table. Since many journals publish online, these tables could be made available to interested readers in the electronic version only.
c) Within group
An advantage of within-subjects designs is that individual differences in subjects' overall levels of performance are controlled. This is important because subjects invariably will differ greatly from one another.
d) obscuring variable.
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