An imbalanced dataset is when you have, for example, a classification test and 90% of the data is in one class. That leads to problems: an accuracy of 90% can be skewed if you have no predictive power on the other category of data! Here are a few tactics to get over the hump: Collect more data to even the imbalances in the dataset. Resample the dataset to correct for imbalances. Try a different algorithm altogether on your dataset. What’s important here is that you have a keen sense for what damage an unbalanced dataset can cause, and how to balance that.