Outliers are data points that deviate significantly from the rest of the data, which can be caused by measurement errors, data entry errors, or natural variations. These outliers can have a negative impact on the performance and accuracy of predictive models, especially those based on linear regression, clustering, or distance-based methods. To handle outliers, you can detect them using statistical tests, box plots, or other methods with criteria such as standard deviation, interquartile range, or z-score. You may also choose to remove outliers from your data; however, this can reduce the size and diversity of your data and introduce bias or errors. Alternatively, you could replace outliers with mean, median, mode, or other values - a more sophisticated and flexible solution but one that can introduce noise or distortion and affect the variance and distribution of your data. Lastly, you can transform outliers using scaling, normalization, or other methods - a more advanced and robust solution but one that can change the shape and distribution of your data and affect the interpretation and meaning of your results.