How scoring works.

After practice, you see an ability score with a range, like 62 ± 5. The score is from 0 to 100. It is our best estimate of how well you are answering the questions in that practice bank.

The ± part shows how sure we are. A narrower range means more answers sit behind the number.

50 is the difficulty of a typical question in that bank. Each bank has its own scale, so a score in one bank does not compare to a score in another.

Your % correct sits under the ability score. It is the share of points you earned.

Two sets of questions can have different difficulty, so the same % can mean different things. The ability score takes the difficulty of each question into account. The % does not.

We show an ability score for a category only after you have answered at least 5 questions in it. Before that, it reads "not enough questions yet".

We use your category results to point you to what to study next.

We don't guess your odds. We show what you know and what to study next.

You will not see a pass-or-fail line, a target score, or a percent chance. Our questions are our own, written to teach. A score on them measures how you did on them. It does not predict how you will do on any other exam.

Every question has a difficulty. We start with the level its author set. As learners answer, we re-measure the difficulty of each question from those answers, using a standard method from test measurement called the Rasch model.

A question that most learners get right moves toward "easier". A question that most learners miss moves toward "harder". Questions with only a few answers stay close to the author's level.

• Answers from fewer than 30 people: we use the starting estimate.
• Answers from 30 to 299 people: provisional.
• Answers from 300 or more people: calibrated.

A score is labeled Provisional while fewer than 80% of the questions behind it are calibrated.

The label says: Provisional: our question difficulties are still being measured from students' answers. The label goes away as more learners answer.

When you are signed in, we store your answers under a one-way hashed version of your account ID. When you are signed out, a random ID made on your device stands in. It isn't linked to your name, email, account or device identifiers.

We use the answers only to measure how hard each question is and to find questions that may be wrong. The privacy policy has the full text.

Smart Drill picks questions near your current level. In Learn mode, it aims for questions you will get right about 7 times in 10. In Exam feel mode, it aims for harder ones, closer to a coin flip.

Missing a hard question does not mean you know less. A harder set can lower your % correct with no change in what you have learned. Look at the trend in your ability score and your weakest categories, not at one session.

Smart Drill is a study tool.