EXERCISE 24 Questions to be Graded
1. What is the r value listed for the relationship between variables 4 and 9? r = -0.32
2. Describe the correlation r = −0.32** using words. Is this a statistically significant correlation? Provide a rationale for your answer.
This represents a moderate negative relationship. It is statistically significant at the 1% level of significance as indicated in the table. (** p < 0.01)
3. Calculate the percentage of variance explained for r = 0.53. Is this correlation clinically important? Provide a rationale for your answer. variance = r^2 = (0.53)^2 = 0.2809 = 28.1%
This is clinically important since any variance over 9% is considered clinically important.
4. According to Table 2, r = 0.15 is listed as the correlation between which two items? Describe this relationship. What is the effect size for this relationship, and what size sample would be needed to detect this relationship in future studies?
This is between variables 3 and 7. It represents correlation between Positive Items and Avoidance. There is a weak correlation here because r < 0.3. The effect size is 0.15. The sample size required in this case would be 273 (given a power of 0.8).
5. Calculate the percentage of variance explained for r = 0.15. Describe the clinical importance of this relationship. variance = r^2 = (0.15)^2 = 0.0225 = 2.25%
This is not considered clinically important since the variance is less than 9%.
6. Which two variables in Table 2, have the weakest correlation, or r value? Which relationship is the closest to this r value? Provide a rationale for your answer.
Variables 6 and 7 have the weakest correlation (r = -0.02). This is the relationship between emotion and avoidance, which are coping styles. The relationship which is closest to this r value is variables 4 and 7, which represents negative items and avoidance. It is