sgmediation2为什么我安装不了啊，求老师指点一下
根据连老师给的这个命令net install sgmediation2, from("https://tdmize.github.io/data/sgmediation2")
他显示如下的结果
PKIX path validation failed: java.security.cert.CertPathValidatorException: vali
> dity check failed
https://tdmize.github.io/data/sgmediation2/ either
  1)  is not a valid URL, or
  2)  could not be contacted, or
  3)  is not a Stata download site (has no stata.toc file).

current site is still http://www.stata.com/