Finding the probability

Please provide comprehensive responses to the following: (a) In the use of a categorical variable with n possible values, explain the following:    1. Why only n – 1 binary variables are necessary    2. Why using n variables would be problematic  (b) Describe how logistic regression can be used as a classifier.(c) Discuss how the ROC curve can be used to determine an appropriate threshold value for a classifier(d) If the probability of an event occurring is 0.4, then    1. What is the odds ratio?     2. What is the log odds ratio?Requirements:- Typed in a word document.- Please write in APA Style and include at least Five (5) reputable sources.- The complete paper should be between 800-to-1000-words.