自由度(DF)
检验自由度 (DF) 可用于确定 P（p 值）。它等于要检验的参数个数。
相关图表工具
常用统计图形在线生成工具：
Pareto Chart
Bar Chart
Box Plot
Histogram
Line Chart
Scatter Plot
Time Series Plot
Function Grapher
Normal Distribution Graph
Normal Probability Plot
实用工具：
Calendar with weeks
Public Holidays by Countries / Regions
Timer & Countdown
Date Calculator
World Clock & Time Zones