Investigators are planning to use PHQ-9 (Patient Health Questionnaire-9) to screen for depression in their study population. PHQ-9 consists of 9 questions, each of which can be scored from 0 (Not at all) to 4 (Nearly every day). The investigators decided to use a summary score of 5 or higher (when summing up the responses from all 9 questions) to indicate that the individual under study has signs of depression (the main outcome in their study). What types of variables should investigators put in their codebook for this outcome?
A. Each of the PHQ-9 questions only (9 variables total).
B. Each of the PHQ-9 questions and variable summing the scores from the 9 questions (10 variables total).
C. Each of the PHQ-9 questions and variable summing the scores from the 9 questions, and the categorization variable (11 variables total)
D.Variable summing the scores from the 9 questions, and the categorization variable (2 variables total)