https://blog.gongquiz.com/2021/07/01/%ec%82%ac%ed%9a%8c%eb%b3%b5%ec%a7%80%ed%96%89%ec%a0%95%ec%97%90%ec%84%9c-%ed%9a%a8%ea%b3%bc%ec%84%b1effectiveness%ec%97%90-%ea%b4%80%ed%95%9c-%ec%84%a4%eb%aa%85%ec%9c%bc%eb%a1%9c-%ec%98%b3%ec%9d%80/