The Decaying Averageformula recognizes that the most recent score is more representative of the student's current mastery level and thus puts more weight on that score (as opposed to a straightaveragethat counts the student's first work and most recent work as equally important). On the other hand, it also recognizes that past work might be relevant; it is still part of the whole picture (as opposed to the Most Recentformula whichonlycounts the most recent score).
How Does it Work?
Let's say you have the Decaying Average 65% formula and 2 scores on Standard A given in this chronological order: 2, 3.
.35(2) + .65(3) =2.65is the Mastery Level.
Next, imagine that you give that student a new score of 4 on Standard A.
.35(2.65) + .65(4) = 3.53 is the new Mastery Level. Notice how this takes the last Mastery Level and weights it by 35%, then weights the most recent score for Standard A by 65%.