Generate a detailed schema and analysis strategy for a Power BI report based on the following criteria: There are multiple students enrolled in various programs, each with a defined start and end date. A student may participate in more than one program and may also receive multiple questionnaires related to those programs. The questionnaires are standardized, consisting primarily of simple yes/no questions and are categorized into five distinct groups. Not all students will complete a questionnaire, nor will all questions be answered. At the conclusion of a specific intervention period, I need to extract a summary of responses, indicating the presence or absence of questionnaires and responses for each question category. The report should clearly illustrate the data structure using a star schema approach, including necessary tables for students, programs, questionnaires, responses, and question categories, while also allowing for the demonstration of missing data where applicable.