…has a lot of variance, then do you think a feature with a low variance will improve your model? NO! To figure out the importance of each feature in a dataset, we use rank correlation.
Some features also have very little variance. If your output has a lot of variance, then do you think a feature with a low variance will improve …
…gher dimensions is a recent problem. These days, data collection and storage has never been easier. More often than not, many datasets have features with similar information. This acts as noise in the system and increases complexity.