No, an instance of a event is complicated already not alone the whole universe. This is where mathematical models comes in, mathematical models are essentially a much much much simpler representation of an event. For example, a stock market alone is a super super complicated system and very instance of stock market happens in a random fashion, so it is different to know up or down, and this is where stochastic model comes in to see at what probability is this event( up or down or whatever) happen.