And while the authors adjusted for body weight, social class and educational level, as well as other differences, and still found a consistent effect, the possibility of bias still remains on any single observational study.
Na wakati waandishi walirekebisha uzito wa mwili, darasa la kijamii na kiwango cha elimu, pamoja na tofauti zingine, na bado wakapata athari thabiti, uwezekano wa upendeleo bado unabaki kwenye uchunguzi wowote wa uchunguzi.