Reference no: EM132595431

Practice Exercise 1: Testing Correlations

Directions: Use the Bivariate Correlation function and the Options submenu to answer each of the questions based on the following scenario.

Scenario:

A researcher is interested in determining if there a relationship between increased police patrols in a neighborhood and a reduction in crime rate? For the neighborhoods in the sample, data concerning the number of police patrols and crimes reported per week was collected for six months.

1. Do correlations allow researchers to make statements about the causal nature of relationships?

2. Write an appropriate null hypothesis for this analysis.

3. What is the mean number of police patrols? What is the mean number of crimes reported?

4. What is the standard deviation for the number of police patrols? What is the standard deviation for the number of crimes reported?

5. Based on the scenario, would you prefer to see a positive or negative correlation?

6. What is the value of the correlation coefficient?

7. Based on the value of the correlation coefficient, how would you classify the strength of this relationship? (refer to Table 5.2 in chapter 5)

8. How are the degrees of freedom determined when testing the significance of a correlation coefficient?

9. Based on the information from the scenario, what is the appropriate value for the degrees of freedom?

10. Does the SPSS output report the value for the degrees of freedom?

11. What is the reported level of significance?

12. Based on the results of the test of significance, is the relationship between the number of police patrols and the number of reported crimes statistically significant?

13. Report and interpret your findings as they might appear in an article.

Practice Exercise 18: Testing Correlations

A recent study examined the relationship between anger levels and blood pressure for males. For each of the 30 male participants, anger level scores were obtained using a scale that could range from 10 to 100 with higher scores indicating higher levels of anger. Additionally, the blood pressure level for each participant was recorded. The following data was collected:

Use the Bivariate Correlation function and the Options submenu to answer each of the questions based on the above scenario.

1. Write an appropriate null hypothesis for this analysis.

2. What is the value of the correlation coefficient?

3. Based on the value of the correlation coefficient, how would you classify the strength of this relationship?

4. Is the correlation coefficient observed for this problem stronger or weaker than the correlation coefficient observed for the relationship between police patrols and crimes reported? Explain your answer.

5. Based on the information from the scenario, what is the appropriate value for the degrees of freedom?

6. What is the reported level of significance?

7. Based on the results of the test of significance, is the relationship between anger and blood pressure statistically significant?

8. Based on your responses to #3 and #4 and the fact that both correlations were statistically significant, what can you conclude about the relationship between practical significance (importance/meaningfulness/strength) and statistical significance (likelihood that a finding is due to chance alone)?

9. Report and interpret your findings as they might appear in an article.