This ratio is independent of several possible alterations to the experimental observations: Adding a constant to all observations does not alter significance.
ðɪs ɹˈeɪʃɪˌoʊ ɪz ˌɪndᵻpˈɛndənt ʌv sˈɛvɹəl pˈɑːsᵻbəl ˌɔltɚɹˈeɪʃənz tə ðɪ ɛkspˌɛɹɪmˈɛntəl ɑːbzɚvˈeɪʃənz: ˈædɪŋ ɐ kˈɑːnstənt tʊ ˈɔːl ɑːbzɚvˈeɪʃənz dʌznˌɑːt ˈɔltɚ sɪɡnˈɪfɪkəns.