Why need to remove outlier?

Answer 1

See related link. Outliers are defined as: In statistics, an outlier is an observation that is numerically distant from the rest of the data. As stated in the related link, outliers should not necessarily be removed from a dataset. If analyses is done, and certain values that are a part of the collected dataset are not included, then the reasons for excluding them from the analyses should be discussed along with the results. Erroneous values that are the result of human or measurement error, such as a particular sensor malfunctioning, may be excluded from analysis, as they are not representative numbers.