AP Physics 5分成绩分析

胡老师

AP Physics 1 and 2: What raw score will be necessary to earn a 5? (Update July 2015, see comments)

Okay, that's the question of the year for 2014-15.  For decades, the raw score to AP score conversion on the Physics B exam has been relatively consistent -- in the neighborhood of 65% for a 5, 50% for a 4, 35% for a 3, 25% for a 2.  I've used those cutoffs in my own class on each of my monthly tests.  Sure enough, students who consistently earn what I call "5s" on my in-class tests tend to earn 5s on the actual AP exam.  

But what's going to happen on the new AP Physics 1 exam?  The style and structure of the Physics 1 exam is substantially different from that of the Physics B exam.  We have no word from anyone at ETS or the College Board about how the score cutoffs might look.   

The actual score cutoffs will be set by a complex data mining process involving statistical wizards at ETS and a committee -- not the test development committee, a different committee -- of high school and college physics teachers.  A College Board representative described the process briefly to the consultants at our weekend meeting.  I didn't quite follow all the details.  Suffice it to say, it's a statistically rigorous process, but one that can't be gamed or anticipated.  We will not know anything real until the summer of 2015, after the first exam adminstration.

So how should an AP Physics 1 teacher set expectations in class this year?  That's going to require a significant amount of guesswork.  We teachers have only a few data points to guide us.  

The first set of data is the previous years' physics B and C exams.  The physics B exam changed significantly in its emphasis in the mid 1990s; yet the cutoff for a 5 remained around 60-65%.  Physics C contains two completely different courses and exams.  Physics C mechanics cutoffs in the 1980s and 1990s were about 10% higher than the E&M cutoffs; since the mechanics exam added more experimental and conceptual questions, and since it placed more emphasis on calculus-based problems in the free response problems, that gap has lowered to essentially nothing in the last two released exams.  On either exam, you now need in the neighborhood of 53-58% to earn a 5.

The AP Physics exams have changed gradually and organically through the years, but the redesign to the new AP Physics 1 and 2 courses will be seismic and unprecedented.

Um, wait... not unprecedented.  The College Board did a similar redesign of the AP Biology course for the 2013 exam; and of the AP Chemistry course for the 2014 exam.  The 2013 AP Bio exam has been administered and scored.  While biology is a completely different animal from physics, perhaps we can draw some lessons in how the cutoff scores changed from 2012 to 2013.

In 2012 (before the redesign), the score cutoffs for AP Bio were:
5 73%
4 63%
3 55%
2 46%

In 2013 (on the redesigned test), the score cutoffs for AP Bio were:
5 77%
4 62%
3 45%
2 25%

Now that I've seen these, I better understand what bio teachers have told me about the new test.  They say (and the College Board confirms) that far fewer students earned 5s on the new exam, far fewer students earned 1s, but more people scored in the middle of the distribution.  That could be a result of the new style and content on the exam, but it could also -- and in my mind, more likely -- merely be a consequence of the higher cutoff score for a 5 and the way, way lower cutoff score for a 2.  We'll see in August whether the AP Chemistry redesign produces a similar scrunching of the bell curve.

To summarize:  Physics B cutoffs have been consistent over decades.  Physics C cutoffs recently have been consistently a bit lower than physics B cutoffs.  The redesigned AP Bio test raised a wee bit the cutoff for a 5, but substantially lowered the cutoff for a 2.

What should you do?  What am I going to do?

Not sure yet.  My gut is still telling me to stick to my current cutoffs for the first year, because these will be close enough.  I do like using cutoff scores that are easy for students to remember: 65%, 50%, 35%, and 25% are nice round numbers. I'll let you know if I end up changing my approach.

From： Jacobs Physics