- Machine Learning with Python
- What is Machine Learning?
- Data Preprocessing in Data Science and Machine Learning
- Feature Selection in Machine Learning
- Train-Test Datasets in Machine Learning
- Evaluate Model Performance - Loss Function
- Model Selection in Machine Learning
- Bias Variance Trade Off
- Supervised Learning Models
- Multiple Linear Regression
- Logistic Regression
- Logistic Regression in Python using scikit-learn Package
- Decision Trees in Machine Learning
- Random Forest Algorithm in Python
- Support Vector Machine Algorithm Explained
- Multivariate Linear Regression in Python with scikit-learn Library
- Classifier Model in Machine Learning Using Python
- Cross Validation to Avoid Overfitting in Machine Learning
- K-Fold Cross Validation Example Using Python scikit-learn
- Unsupervised Learning Models
- K-Means Algorithm Python Example
- Neural Networks Overview

# Bias Variance Trade Off

The interesting property of a machine learning model is its capacity to predict or categorize new unseen data (data that was not used in training the model). For this reason the important measure is the MSE error with test data, which is denominated as **test MSE**. The goal is to choose a model where the **test MSE** is the lowest across other models.

The ** bias variance tradeoff** is generated when at some point if we increase the bias of the model by creating additional features, the variance of the model increases too (overfitting), and on the other hand if the model is too simple (has very few parameters), it will have high bias and low variance (under fitting).

It is necessary to find the right balance between bias and variance without overfitting and under fitting the data. The prediction error in a Supervised machine learning algorithm can be divided into three different parts:

- Bias Error
- Variance Error
- Irreducible Error

First we will write the equation which breaks these three factors:

**Variance Error**

The first term on the right hand side is the variance of the estimation across many testing sets. This measures the average model deviation among different testing data. In particular, a model with high variance is suggestive that it is overfit to the training data. In this scenario, the model is capturing the noise of the training dataset but it is poor for new data.

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