Which of the following statements is incorrect?

a To identify mixed costs when using regression analysis, dummy variables can be used.

b In regression analysis, statistical tests must be employed to determine the statistical significance of the estimated relationship.

c A coefficient of determination of 0 for a simple linear regression always means that there is no statistical relationship between two variables.

d The percentage of the dependent variable explained by the independent variables is the coefficient of determination.

e The coefficient of determination is the ratio of the explained sum of squares to the total sum of squares. pg96