Detailed Case,Theory & Numeric Problems-20 Questions - Sample Size, Effect Size, Power Analysis, Hypothesis & Non-Parametric Tests (Ex 13, JUS 302 Ch 9, t test, G*Power, ANOVA, SPSS, etc)

EXERCISE 12 Questions to be Graded

RESEARCH ARTICLE 2

Source: Voss, J. A., Good, M., Yates, B., Baun, M. M., Thompson, A., & Hertzog, M. (2004). Sedative music reduces anxiety and pain during chair rest after open-heart surgery. Pain, 112 (1–2), 197–203.

Introduction

Voss et al. (2004) conducted a study to determine the “effectiveness of non-pharmacological complementary methods (sedative music and scheduled rest) in reducing anxiety and pain [sensation and distress] during chair rest” (Voss et al., 2004, p. 197) after open-heart surgery. The subjects receiving the treatment of sedative music had significantly less anxiety, pain sensation, and pain distress than those subjects in the scheduled rest and the standard care group. The researchers recommend the use of sedative music as an adjuvant to medication for management of anxiety and pain in postoperative patients. The study only involved patients who had had open-heart surgery, which limits the generalization of the findings. Future research is needed to test the effects of music on the anxiety and pain of different types of patients. In addition, research is needed to determine the optimal length for the music sessions and the effectiveness of repeat music sessions in reducing anxiety and pain.

Relevant Study Results

“An experimental, pretest and posttest three-group design was used for this randomized clinical trial. A convenience sample of 62 patients was obtained from a surgical intensive care unit at a rural midwestern hospital over a period of 6 months in 2002. … The planned sample size of 96 patients (30 per group plus 6 for attrition) was based on power analysis with an estimated medium effect size of 0.33, power 0.80, alpha = 0.05 and repeated measures analysis of variance. However, preliminary analyses after 62 patients were enrolled revealed significant group differences and large effect sizes for anxiety, pain sensation, and pain distress; thus the data collection was concluded” (Voss et al., 2004, p. 198).

1. How large a sample was needed for the Voss et al. (2004) study according to the power analysis? Was this the minimum sample size needed for the study, or did the researchers allow for sample mortality?

2. What was the sample size for the Voss et al. (2004) study? Was this sample size adequate for this study? Provide a rationale for your answer.

3. What effect size was used in conducting the power analysis for this study? What effect size was found during data analysis, and how did this affect the sample size needed for this study?

4. What power was used to conduct the power analysis in the Voss et al. (2004) study? What amount of error exists with this power level? Provide a rationale for your answer.

5. If researchers set the power at 90% to conduct their power analysis, would there be less or more chance of a Type II error than setting the power at 80%? Provide a rationale for your answer.

6. If researchers set the alpha (α) for their study at 0.001 versus 0.05, would they need a smaller or larger sample size? Provide a rationale for your answer.

7. In the discussion section of the research article, the authors stated that sedative music had a large effect size when compared to both usual chair rest (>1.0) and scheduled chair rest (>0.9). Furthermore, scheduled chair rest when compared with usual chair rest did not result in significantly less anxiety, pain sensation, or pain distress, but the differences were in the expected direction with small to medium effects (0.20 to 0.45). Why is this information important for future research?

8. Based on the information provided in Question 7, what effect size(s) would researchers use in conducting a similar study? Provide a rationale for your answer.

9. If a researcher conducted a two-tailed t-test versus a one-tailed t-test, would they need a smaller or larger sample size? Provide a rationale for your answer.

10. Should the findings from the Voss et al. (2004) study be used in clinical practice? Provide a rationale for your answer.