Attached below are three methods used by ManageBac to perform term grade calculations.
I do understand how each method is applied but I am not sure why they yield different answers. Could someone please explain why.
Personally, I believe the first approach is the correct one because the average for each assessment is calculated separately.
Thanks in advance for any help you can offer.
They give different answers because they use different calculations in two ways.
The first and third methods treat each subtask within a task as equivalent, while the second method treats each potential mark within a task as equivalent. So on the first subtask you can have $\dfrac{\tfrac{17}{20}+\frac{1}{4}}{2} =0.55$ or have $\dfrac{17+1}{20+4}=0.75$ as the score for the first subtask; if you do better on the subtask with more potential marks, then the second method gives you a higher score.
The first and second methods weight the tasks in the ratios $30\%:20\%:50\%$ (or $3:2:5$ or $6:4:10$) while the third method weights the subtasks in the ratios $3:3:2:2:5:5:5$; the third method is equivalent to weighting the tasks $6:4:15$ or $24\%:16\%:60\%$, giving the last task an even higher weighting because it has more subtasks than the others. So if you did better on the last task than the others then the third method gives you a higher overall score than the first method does.