E-Text Week 5 Team A
RES/342

E-Text Week 5 Team A
Chapter 12 Review # 1 (a) How does correlation analysis differ from regression analysis? (b) What does a correlation coefficient reveal? (c) State the quick rule for a significant correlation and explain its limitations. (d) What sums are needed to calculate a correlation coefficient? (e) What are the two ways of testing a correlation coefficient for significance?
Answer:
a) The correlation analysis identifies the relationship between two variables of interest. The regression analysis uses one or more independent variables (x) to predict the value of the dependent variable (y) using a scatter plot to view the relationships to each other. b) The correlation coefficient reveals the degree of association between independent and dependent variables. The values are between r = -1 and r = 1 and show if the strength is negative or positive. c) |r| >2/n This is the quick 5% rule for significance. It is based on the fact that two-tail t-values for α = .05 usually are not far from 2. The quick rule is exact for ν = 60 and does not work well if the ɳ is too small. d) The sum of x and the sum of y and multiply each value x-value by its corresponding y-value to find the sum. e) Test for zero correlation: t=r n-21- r2
The critical value for a correlation coefficient: ra = tata2+ n-2
12.48 In the following regression, X = weekly pay, Y = income tax withheld, and n = 35 McDonald’s employees. (a) Write the fitted regression equation. (b) State the degrees of freedom for a two tailed test for zero slope, and use Appendix D to find the critical value at α = .05. (c) What is your conclusion about the slope? (d) Interpret the 95 percent confidence limits for the slope. (e) Verify that F = t2 for the slope. (f) In your own words, describe the fit of this regression.
Answer:
a) y =