Posted: September 16th, 2017
Exercise 31 graded question
Instructions
Review Exercise 31 in Statistics for Health Care Research: A Practical Workbook.
Complete the Study Questions in Exercise 31. Compare your answers to the Answers to Study Questions.
Complete Exercise 31: Questions to be Graded on pages 235-236 and submit as directed by the instructor.
In order to receive full credit on calculated answers, please show your work. (Use Word’s equation editor, etc., and/or provide a short written description as to how you obtained the final result.)
Relevant Study Results
A total of 25 women were enrolled in the health-promotion program and 21 subjects completed the program with three sets of outcome assessments at pretest, 3 months, and 6 months. The mean age of the subjects was 77 years, and 90% of them had been diagnosed with one or more chronic diseases. The significance level of the study was set at α = 0.05. The results from the study are presented in the two tables that follow. Table 2 describes the health-promotion program’s effects on cardiovascular risk factors, and Table 3describes the effects on health behaviors. The third dependent variable of this study was life satisfaction, which was significantly improved from pretest to the end of the health-promotion program at 3 months and at 6 months follow-up.
TABLE 2 Program Effects on Cardiovascular Risk Factors
* p< 0.05.
a Paired t-test results between the pretest and 3-month measures.
b Paired t-test results between the pretest and 6-month measures.
TABLE 3 Program Effects on Health Behaviour
* p< 0.05.
a Paired t-test results between the pretest and 3-month measures.
b Paired t-test results between the pretest and 6-month measures.
STUDY QUESTIONS
1. What clues do you have that this study had “dependent groups?”
2. Which t ratio or value in Table 3 is the greatest for the 6-month follow-up? Which variable is being examined for differences between the pretest and 6-month follow-up by this t ratio?
3. Which t ratio or value listed in Table 2is the smallest in determining the difference between the pretest and 6-month follow-up? This t ratio was calculated to determine the change in which variable from pretest to 6 months after the intervention?
4. t= −0.93 is the result for what variable in this study? Is this t ratio significant? Provide a rationale for your answer.
5. Compare the pretest to 3 months and 6 months t ratios for BMI from Table 2. What is your conclusion regarding the effects of the health-promotion intervention on the BMI long term?
6. The t-test for dependent groups is conducted in research for what purpose?
7. What is the smallest, significant t ratio listed in Table 3? Provide a rationale for your answer.
8. Why do you think that the smaller t ratios are not statistically significant?
9. How would you describe the result t = −1.45 in this study?
ANSWERS TO STUDY QUESTIONS1. This study was conducted using a one group pretest-posttest design in which the subjects serve as their own control. The subjects’ outcomes at 3 and 6 months were compared with their pretest values. The single sample pretest-posttest design indicates that the groups were dependent or related. In Tables 2 and 3the t-tests are identified as paired t-tests, which are conducted on dependent groups.
2. t= −3.93 (Exercise) is the largest t ratio at 6 months, as listed in Table 3.
3. t= −0.80 (BMI) represents the smallest t-ratio at 6 months, as listed in Table 2.
4. t= −0.93 indicates the difference in Diet behavior from pretest to 3 months. This t-ratio does not have an asterisk (*) next to it in Table 3; therefore, it is not statistically significant. The asterisk directs the reader to the footnotes at the bottom of the table where the asterisk is said to represent p< 0.05, the least stringent acceptable value for statistical significance.
5. t= 3.44* (3 months) and t = −0.80 (6 months). At 3 months, the difference in BMI (body mass index) from pretest was statistically significant with t= 3.44*, p< 0.05. At 6 months, the difference in BMI from pretest was no longer statistically significant with t = −0.80. These results indicate that although initially the BMI decreased significantly from the pretest (mean = 22.7) to 3 months (mean = 22.1), the BMI actually increased at 6 months (mean = 22.9). Thus, the health-promotion intervention did not have a positive long-term effect on the subject’s BMI, since the subjects demonstrated an increase in BMI versus a decrease.
6. The t-test for dependent groups is conducted to determine statistical differences between two related or dependent groups. The t-test can be used to determine differences between two dependent groups following a treatment and also for comparing and contrasting two groups for a selected variable. Paired t-test is another name for the t-test for dependent groups.
7. t= −3.02*, p< 0.05 is the smallest significant t ratio listed in Table 3. The −3.02 is the smallest tratio with an *, indicating that Total health behavior was statistically significant from pretest to 3 months in this study at p< 0.05.
8. The small t ratios indicate small relative differences between the two groups that are usually not statistically significantly different, especially in small sample studies. The larger the calculated t ratios, the smaller the observed p values and the more likely one will reject the null hypothesis, since the groups are significantly different.
9. The result t = −1.45 indicates that there is no statistically significant difference in Smoking behavior from pretest to 3 months in this sample. Thus, the null hypothesis would be accepted, which states the health-promotion intervention did not have an effect on Smoking behavior.
Name:____________________________________________ Class: ____________________
Date: _________________________________________________________________________________
□ EXERCISE 31 Questions to be Graded
1. What are the two groups whose results are reflected by the t ratios in Tables 2 and 3?
2. Which t ratio in Table 2 represents the greatest relative or standardized difference between the pretest and 3 months outcomes? Is this t ratio statistically significant? Provide a rationale for your answer.
3. Which t ratio listed in Table 3represents the smallest relative difference between the pretest and 3 months? Is this t ratio statistically significant? What does this result mean?
4. What are the assumptions for conducting a t-test for dependent groups in a study? Which of these assumptions do you think were met by this study?
5. Compare the 3 months and 6 months t ratios for the variable Exercise from Table 3. What is your conclusion about the long-term effect of the health-promotion intervention on Exercise in this study?
6. What is the smallest, significant t ratio listed in Table 2? Provide a rationale for your answer.
7. Why are the larger t ratios more likely to be statistically significant?
8. Did the health-promotion program have a statistically significant effect on Systolic blood pressure (BP) in this study? Provide a rationale for your answer.
9. Examine the means and standard deviations for Systolic BP at pretest, 3 months (completion of the treatment), and 6 months. What do these results indicate? Are these results clinically important? Provide a rationale for your answer.
10. Is this study design strong or weak? Provide a rationale for your answer.
BONUS QUESTIONWould you, as a health care provider, implement this intervention at your facility based on the Total Risk Score results? Provide a rationale for your answer.
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