What I have to do?
Two courses (A and B) students CGPA and percentage of class attendance is given. I have to compare CGPA of two groups (group is based on attendance - high vs low) regarding students of each course. Some of the students of course A are not enrolled in the course B, that is, all of the students of course A and course B are not same.
So, What creates the problem?
Since all the students of two courses are not same, that is, CGPA data set is not same in each of the courses, will I have to correct p values for each comparison test of CGPA?
Update - to clear the problem
What is the nature of my data?
I am using actual data, that is, no data is collected from the students. Each course attendance is independent of each other. e.g. Attending course A class lectures does not ensure attendance of same student in course B, even if that student is enrolled in both of the courses. Moreover, I do not expect that course difficulty will have impact on class attendance.
Which type of statistical test I am using and how?
I am using standard T test. Reason of using T Test is, I assume normally distribution using Using Central Limit Theorem. When two groups (high and low) of data was found not having equal variances, I used Welch's T Test as suggested by this.
For each course, I used T test dividing the students into two groups - how and low attendant. Top one third percentile was considered as high attendant and bottom one third percentile was considered as low attendant as done this research in dividing Facebook users into two categories - high and low.
What is my hypothesis?
CGPA of the high and low attendant of classes differs significantly regardless the course.