Ichi chichava waishandiswa okuwedzera pamusoro zvinogona zvaitika asingaputsi; mamwe mashoko, ona Morgan and Winship (2014) uye Imbens and Rubin (2015) . The okuwedzera ataure mazano anotevera ari mashoko dzingangovapo zvaitika:
The okuwedzera achasanganisirawo nokuenzanisa pakati-nyaya, mukati-nyaya, uye yakavhenganiswa mazano. The okuwedzera Angasanganisira mashoko pakushandisa pre-kurapwa mashoko akagadzira kana kuongorora.