the grades in each class on a test were:Morning class = 62, 67, 71, 74, 76, 77, 78, 79, 79, 80, 80, 81, 81, 82, 83, 84, 86, 89, 93, 98

Afternoon class = 81, 82, 83, 84, 85, 86, 87, 87, 88, 88, 89, 89, 89, 90, 90, 90, 90, 91, 91, 91, 92, 92, 93, 93, 94, 95, 96, 97, 98, 99

The mean for the morning class is 80 and the mean of the afternoon class is 90. The unweighted mean of the 80 and 90 is 85, so the unweighted mean of the two means is 85. However, this does not account for the difference in number of students in each class (20 versus 30); hence the value of 85 does not reflect the average student grade (independent of class)

this does not account for the difference in number of students in each class---> what does this line mean? i get it that 80 is the avg marks of

**per student**in class A and 90 of per student in class B. so mean of avg marks of A & B= (80+90)/2

**That means i am considering the average marks of one student from class A (weight of 80=1), not considering the marks of remaining 19 and same goes for class b considering the average marks of one student from class B, not considering the marks of remaining 29**

@Dr.Peterson