ðɪs ˈɔfən mˌeɪks ɪt dˈɪfɪkəlt tʊ ɐtɹˈɪbjuːt pˈɑːzᵻtˌɪv ɔːɹ nˈɛɡətˌɪv ˈaʊtkʌmz tʊ ˌɛni wˈʌn ʌvðə spəsˈɪfɪk tɛknˈiːks.
This often makes it difficult to attribute positive or negative outcomes to any one of the specific techniques.