hospitality and tourism, management homework help

Himy major is hospitality and tourism. i have to do a research on (customers' attitude  toward non-tipping restaurants a new trend in the restaurant industry) . I have to answer these questions and i would like to receive help from you. My questions are these 2 mentioned here. Excuse me, please give me exactly based on APA style. 1) why the results from previous studies can not be directly applied in this study?2) how the results of this study help managers or operation?thank you .