BackgroundAlthough guidelines suggest that older adults engage in regular physical activity (PA) to reduce heart disease, surprisingly few studies have evaluated this relationship, especially in those >75 years. The researchers wanted to find out whether heart disease was lower among those who had high levels of physical activity compared to those who had low levels of physical activity.

Methods and ResultsAnalysis among 4207 US men and women of a mean age of 73 years (standard deviation=6) who were free of CVD at the start of the study. PA (assessed as low, moderate, and high) was measured in all participants at the beginning of the study. New heart disease events (yes/no) was assessed from medical records. A total of 1182 heart disease events were noted. The researchers found that greater physical activity was negatively associated with heart disease, even in those 75 years. For example, in comparison with a low physical activity, those in the high category had a lower risk of heart disease (IPR* = 0.50; 95% confidence interval, 0.38-0.67).

ConclusionsThese data provide evidence supporting physical activity recommendations to reduce the incidence of heart disease among older adults.

*IPR = incidence proportion ratio (same as risk ratio, RR)

1. What is thedependentvariable in the study?

1. Older adults
2. Heart disease
3. Gender
4. Physical activity

2. What is theprimary independent(explanatory) variable in the study?

1. Older adults
2. Heart disease
3. Gender
4. Physical activity

3. What type ofmeasurementis physical activity as described above?

1. Continuous
2. Ordinal
3. Nominal
4. Binary (dichotomous)

4. What type ofmeasurementis heart disease as described above?

1. Continuous
2. Ordinal
3. Nominal
4. Binary (dichotomous)

5. What type of measurement is age as described above?

1. Continuous
2. Ordinal
3. Nominal
4. Binary (dichotomous)

6. Based on the excerpt above, what is one way of stating an alternative hypothesis that was tested regarding physical activity and heart disease?

1. Heart disease is more common among those with high physical activity compared to those with low physical activity.
2. Heart disease is less common among those with high physical activity compared to those with low physical activity.
3. Heart disease is the same among those with high physical activity compared to those with low physical activity.
4. None of the above

7. Based on the results of the study, is the relationship between physical activity and heart disease statistically significant?

1. Yes
2. No

8. Based on the results of the study, what is the direction of the association between physical activity and heart disease?

1. Positive
2. Negative
3. Null
4. None of the above

9. In this study, what measure of heart disease did the investigators use?

1. Incidence
2. Prevalence
3. None of the above

10. What type of hypothesis test best describes the one the researchers conducted:

1. One-sample test of means
2. Independent test of means
3. One sample test of proportions
4. Comparing two proportions

11.The "plus-four" method for p used when calculating a confidence interval for a proportion is used when n is large.

1. True
2. False

12.When calculating the sample size needed to achieve a certain margin of error, we find that the larger the sample size the smaller the margin of error

1. True
2. False

Use this information to answer questions 13 - 19.

In a study to examine whether oat bran was more effective than cornflakes in reducing the risk of diabetes, investigators enrolled participants and assigned some to the oat bran group and the others to corn flakes, and obtained the incidence proportion ratio of diabetes, comparing oat bran to cornflakes.

13.If the incidence proportion ratio of diabetes, comparing the oat bran to cornflakes was > 1 (e.g., 2.5), what type of relationship would that be?

1. Positive
2. Negative
3. Null

14. Assume the incidence proportion ratio comparing oat bran to cornflakes was 0.55. How would this be expressed in terms of a percentage?

1. 55% lower
2. 45% lower
3. 55% higher
4. 45% higher

15.If the point estimate and 95% confidence interval for the incidence proportion ratio comparing oat bran to corn flakes were 0.55 (0.35 - 2.35), would this represent a statistically significant association?

1. Yes
2. No

16. What would represent a null relationship in terms of the incidence proportion ratio?

1. IPR<0
2. IPR>0
3. IPR=0
4. IPR=1

17.If the point estimate and 95% confidence interval for the incidence proportion difference comparing treatment to placebo were 0.96 (0.75 - 1.80), would this represent a statistically significant association between the treatment and nausea?

1. Yes
2. No

18.What would represent a null relationship in terms of the incidence proportion difference (IPD)?

1. IPD<0
2. IPD>0
3. IPD=0
4. IPD =1

19.If the point estimate and 95% confidence interval for the incidence proportion ratio of diabetes comparing bran flakes to cornflakes were 0.56 (0.46 to 0.66), would this represent a statistically significant association?

1. Yes
2. No

20. Which of the following statements is/are true?

1. When comparing the means of two independent populations, you use a t-test
2. When comparing the means of two independent populations, you use a z-test
3. When comparing the proportions of two independent populations you use a t-test
4. All of the above are true.

21. Which of the following statements regarding p-value istrue?

1. It is the probability of the observed test statistic or one more extreme, assuming the null is true.
2. It is the probability of the null hypothesis being true.
3. Large p-values provide strong evidence against the null hypothesis.
4. All the above are true.

22. Which of the following does not describe the variability of data?

1. Median
2. Standard Deviation
3. Skewness
4. Kurtosis
5. All of the above measure variability

23. The mean is resistant to skew and outliers.

1. True
2. False