# Topic 2

**Topic 2 DQ 1**

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**Explain the importance of random sampling. What problems/limitations could prevent a truly random sampling and how can they be prevented?**

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**Topic 2 DQ 2**

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**Explain each sampling technique discussed in the “Visual Learner: Statistics” in your own words, and give examples of when each technique would be appropriate.**

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**Exercise 10**

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1. What demographic variables were measured at the nominal level of measurement in the Oh et al. (2014) study? Provide a rationale for your answer.

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2. What statistics were calculated to describe body mass index (BMI) in this study? Were these appropriate? Provide a rationale for your answer.

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3. Were the distributions of scores for BMI similar for the intervention and control groups? Provide a rationale for your answer.

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4. Was there a significant difference in BMI between the intervention and control groups? Provide a rationale for your answer.

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5. Based on the sample size of N = 41, what frequency and percentage of the sample smoked? What frequency and percentage of the sample were non-drinkers (alcohol)? Show your calculations and round to the nearest whole percent.

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6. What measurement method was used to measure the bone mineral density (BMD) for the study participants? Discuss the quality of this measurement method and document your response.

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7. What statistic was calculated to determine differences between the intervention and control groups for the lumbar and femur neck BMDs? Were the groups significantly different for BMDs?

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8. The researchers stated that there were no significant differences in the baseline characteristics of the intervention and control groups (see Table 2). Are these groups heterogeneous or homogeneous at the beginning of the study? Why is this important in testing the effectiveness of the therapeutic lifestyle modification (TLM) program?

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9. Oh et al. (2014, p. 296) stated that ???the adherence rate to the TLM program was 99.6%.??? Discuss the importance of intervention adherence, and document your response.

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10. Was the sample for this study adequately described? Provide a rationale for your answer.

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**Exercise 26**

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1. Plot the frequency distribution for ???Age at Enrollment??? by hand or by using SPSS.

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2. How would you characterize the skewness of the distribution in Question 1???positively skewed, negatively skewed, or approximately normal? Provide a rationale for your answer.

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3. Compare the original skewness statistic and Shapiro-Wilk statistic with those of the smaller dataset ( n = 15) for the variable ???Age at First Arrest.??? How did the statistics change, and how would you explain these differences?

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4. Plot the frequency distribution for ???Years of Education??? by hand or by using SPSS.

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5. How would you characterize the kurtosis of the distribution in Question 4???leptokurtic, mesokurtic, or platykurtic? Provide a rationale for your answer.

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6. What is the skewness statistic for ???Age at Enrollment???? How would you characterize the magnitude of the skewness statistic for ???Age at Enrollment????

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7. What is the kurtosis statistic for ???Years of Education???? How would you characterize the magnitude of the kurtosis statistic for ???Years of Education????

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8. Using SPSS, compute the Shapiro-Wilk statistic for ???Number of Times Fired from Job.??? What would you conclude from the results?

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9. In the SPSS output table titled ???Tests of Normality,??? the Shapiro-Wilk statistic is reported along with the Kolmogorov-Smirnov statistic. Why is the Kolmogorov-Smirnov statistic inappropriate to report for these example data?

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10. How would you explain the skewness statistic for a particular frequency distribution being low and the Shapiro-Wilk statistic still being signifi cant at p < 0.05?

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