Data Mining tasks
Predictive tasks:
---Classification (which is used for discrete target variables)
---Regression (which is used for continuous target variables)
Descriptive tasks:
---Association analysis (to discover patterns that describe strongly associated features in the data)
---Cluster analysis (to find groups of related observations)
---Anomaly detection (identify observations whose characteristics are significantly different from the rest of the data)
Types of Attributes
---Nominal
Examples: ID numbers, eye color, zip codes
---Ordinal
Examples: rankings (e.g., taste of potato chips on a scale from 1-10), grades, height in {tall, medium, short}
---Interval
Examples: calendar dates, temperatures in Celsius or Fahrenheit.
---Ratio
Examples: temperature in Kelvin, length, time, counts
bias是classifier产生的（比如分类器建立在一些假设条件基础上）
variance由数据集的选取产生
noise数据集的某个数据产生