数据缺省 Missing values

One may choose to either omit elements from a dataset that contain missing values or to impute a value.

特殊值 Special values

Numeric variables are endowed with several formalized special values including ±inf, NA and NaN. Calculations involving special values often results in special values, and need to be handled/cleaned.

异常值 Outliers

They should be detected, but not necessarily removed. Their inclusion in the analysis is a statistical decision.

明显不一致值 Obvious inconsistencies

A person’s age cannot be negative, a man cannot be pregnant and under-aged person cannot possess a drivers license.