1) research question: does the presence of a birth doula during childbirth in the hospital reduce the chance of postpartum depression and stress in mothers? 2) research method: experimental. 3) variable 1 is presence of a doula. what kind of variable is it and why? options: discrete, continuous, nominal interval, ration, person variable, concrete variable or hypothetical construct? explain 4) variable 2 is the presence of postpartum depression and stress. what kind of variable is it? same options as above and, please, explain why