Explain briefly the meaning of: a. Categorical variables. b. Qualitative variables. c. Analysis-of-variance (ANOVA) models. d. Analysis-of-covariance

Question:

Explain briefly the meaning of:
a. Categorical variables.
b. Qualitative variables.
c. Analysis-of-variance (ANOVA) models.
d. Analysis-of-covariance (ANCOVA) models.
e. The dummy variable trap.
f. Differential intercept dummies.
g. Differential slope dummies.