Power analysis can assist in study design by determining what sample size would be required in order to have a reasonable chance of rejecting the null hypothesis when the alternative hypothesis is true.
pˈaʊɚɹ ɐnˈæləsˌɪs kæn ɐsˈɪst ɪn stˈʌdi dɪzˈaɪn baɪ dɪtˈɜːmɪnɪŋ wʌt sˈæmpəl sˈaɪz wʊd biː ɹᵻkwˈaɪɚd ɪn ˈɔːɹdɚ tə hæv ɐ ɹˈiːzənəbəl tʃˈæns ʌv ɹᵻdʒˈɛktɪŋ ðə nˈʌl haɪpˈɑːθəsˌɪs wɛn ðɪ ɔːltˈɜːnətˌɪv haɪpˈɑːθəsˌɪs ɪz tɹˈuː.