who is the model model for survival how can i test the survival model how to model duration how to fit survival model when do you know a duration when can a survival model be used how to design a robust survival model what is an uncertain duration? how are survival models based on data how does an event start and end when does a random spell start and ends which term describes the time at which each spell begins? how to find the exact time a duration of the survey has ended how to find the duration of a spells when is a duration model of a survival model how to design and model simulations how do we determine the duration of a spell what is the model used for survival studies when does a survey start is the duration of the survey the same as the specific period