Proposed data collection methods

Say for example, if I were to conduct a Cross-sectional study of Employees, Supervisors and Managers within the same organisation with each sample group consisting of 10 people and I gave them a Likert Questionnaire (five point scale, 1=Strongly Disagree 2=Disagree 3=Neutral 4=Agree 5= Strongly Agree), which was broken down into 3 sets of 10 questions on different topics (exactly the same for each group), how could I justify the why and the how as the proposed as the best method to collect data.