# Summary

Summarize what we have learned in this chapter.

In this chapter, we learned about the following concepts.

## Bias-variance trade-off review

Bias-variance trade-off is very important to improve the model performance. The main goal here is to visually explore the idea of bias and variance in modeling and understand the importance of their trade-off.

## Morale function and model error

Plotting the true function for the generated data results in different sources of errors:

The irreducible error occurs from an imperfect ability to measure morale because of some unavoidable reasons.

The bias error occurs from an imperfect relationship between time and morale.

The variance error occurs from an insufficient amount of good data that can correctly quantify the relationship(s).

These errors combine, resulting in the final error in our trained model.

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