Changing AP score cutoffs now that the guessing penalty is gone

In early June, the College Board released the news that, starting next year, the raw score for an AP multiple choice section will be the total number of correct questions, without a "guessing penalty."  You first heard it here, on the Jacobs Physics blog.

One of my major recommendations to AP physics teachers is to make ALL classroom tests in AP format.  This means use authentic AP questions, give the appropriate amount of time for each (one minute per point free response, 7 multiple choice every 9 minutes)... and use a scale converter to translate each student's grade into an approximate AP score.

In past Physics B exams, it's taken roughly 65% of the available points to get a 5, 50% to get a 4, and 35% or so to get a 3.  That exact conversion fluxuates year-to-year depending on the difficulty of that year's exam, but this was a good rule of thumb.  Problem is, now that the subtraction of 1/4 point for each wrong multiple choice question is gone, raw scores will be higher.  How will these numbers change?

The calculation is not quite as simple as it initially might look.  Scores of the weaker students will improve more than those of stronger students, because weaker students will miss more questions and thus fail to be penalized for "guessing" more often.  And free response scores will not go up, only multiple choice.  This all points to adding a bit to each score cutoff, with more being added to the lower cutoffs.

This year, I'm going to use these cutoffs in my class.  I'll see if they work... and I'll appreciate feedback, as well:

5  68%

4  55%

3  41%

2  30%

We'll only know more through experience, and when another released exam comes out.

GCJ

New Guidance for Free Body Diagrams on the AP Exams!

Some families argue politics or religion.  AP Physics readers have been arguing free body diagrams.

Many good teachers have differing opinions about the purpose and proper construction of the free body diagram.  The grading of free bodies on the AP exam has been the subject of extremely lively debate for many years.  Everyone, fortunately, has common goals:

* Award credit to students for correct physics

* Do NOT award credit to students for vague or incorrect physics

* Have enough flexibility in the rubric to accomodate alternative but reasonable interpretations of the correct construction of the free body diagram.

Perhaps the loudest of the shouting involves the issue of vector components.  Many of us -- including me -- take it as a matter of faith that a free body should never include components of a force.  Others reasonably point out that since the whole point of the diagram is to determine the magnitudes of the forces, and since one must break down angled vectors into components at some point, such components represent a necessary and important part of problem solving technique.  I see the legitimacy to both arguments. 

In order to quiet the arguments and send a clear message about free body components, the AP development has decided to change the language used to ask students to draw free body diagrams.  The test questions now will SPECIFICALLY forbid components on free body diagrams, and will even remind students to use a separate space to draw components where necessary.  You can see the white paper issued by the development committee here within the College Board's website.

Moral of the story:  Argument settled by fiat.  DO NOT put components on free body diagrams, or you will lose points.  Break angled vectors into components on a diagram separate from the initial free body.