Final answer:
There are several factors that can contribute to issues with predictions made by a model, such as individuals not always acting in the same way and the presence of bad data. Additionally, unrealistic assumptions made by the model can also affect its accuracy.
Step-by-step explanation:
The prediction of a model can be erroneous due to several reasons. Firstly, individuals may not always act in the same way, which can lead to inaccurate predictions.
Secondly, bad data, such as when people lie to pollsters, can also affect the accuracy of predictions. Lastly, a model may make assumptions that are not likely to be true in the real world, making it harder to use in practice.