A model is an estimate or approximation of a data set. In the real world, there are too many variables to know exactly what will happen. However, if a model is a good fit, then it can be used to make predictions about what will happen. With a useful model, a predicted value should be a good estimate of an observed value. What did you include in your response? Check all that apply. A model is an estimate of a data set. A useful model can be used to make predictions. Predictions should be a good estimate of what will actually happen.