Class imbalance is a common problem in machine learning. Here's 2 years of knowledge in 2 minutes. Let's go! 1. Class imbalance: Class imbalance is a common problem in machine learning, especially in the context of classification tasks. It occurs when the number of instances of one class (or multiple classes) in a dataset is significantly higher or lower than those of the other classes. 2. Model Bias: The learning model may become biased towards the majority class, leading to poor performance on the minority class. For example, if you're building a fraud detection system and non-fraudulent transactions greatly outnumber fraudulent ones, the model might lean towards predicting non-fraud most of the time. 3. Evaluation Metrics Misleading: Traditional metrics like accuracy can be misleading. In the fraud detection example, a model that always predicts 'non-fraud' might appear highly accurate but is useless. 4. Overfitting to Majority Class: Models might overfit to the majority class and fail to capture the characteristics of the minority class. 5. Addressing Class Imbalance: To address class imbalance, various strategies are used, such as: 6. Undersampling/Oversampling: Balancing the dataset by undersampling the majority class or oversampling the minority class. 7. Synthetic Data Generation: Using techniques like SMOTE (Synthetic Minority Over-sampling Technique) to generate new, synthetic examples of the minority class. 8. Why I DO NOT Adjust for Class Imbalance: One problem with adjusting the class imbalance is that you are altering the data. Applying "Model Calibration" to the machine learning model is a different technique, adjusting the model's predicted probabilities to reflect the true likelihood of an outcome better. 9. Model Calibration: Some common methods for calibrating models are Platt Scaling, Isotonic Regression, and Ensemble Calibration. I'll cover these in another post soon! You now know more about Class Imbalance. But, there's a lot more to learn to become an elite business data scientist. === Ready to learn Data Science for Business? I put together a free on-demand workshop that covers the 10 skills that helped me make the transition to Data Scientist: learn.business-science.io/fr… And if you'd like to speed it up, I have a live workshop where I'll share how to use ChatGPT for Data Science: learn.business-science.io/re… If you like this post, please reshare ♻️ it so others can get value.