统计学covariance, correlation coefficient

问题描述:

统计学covariance, correlation coefficient
统计学上 covariance, correlation coefficient是什么意思,能否举例说明?,如果mortgage rate 和number of houses sold 的correlation coefficient是-0.909,那么他们是什么关系呢?可否除了negative relationship以外说的详细点

关系:strong negative correlation
slope is negative and their linear relationship is very strong.
var(a+b)=var(a)+var(b)+2cov(a,b)