Equated Percent Correct (EPC)
The Equated Percent Correct (EPC) helps you understand how well you are performing relative to a standardized exam or a complete question bank. Unlike raw percent correct, EPC adjusts for question difficulty and relevance to give a more accurate picture of exam readiness.
What is the Equated Percent Correct?
It is an estimate of the percentage of content you have mastered, adjusting for differences in question difficulty and relevance (i.e., the frequency of appearance of topics covered by a question).
Depending on your Study objective, EPC is interpreted slightly differently.
- For Study objectives USMLE Step 1 and Step 2 CK, the EPC answers the question: “What percentage of questions would I answer correctly on a standardized exam today?"
- For all other study objectives, it answers the question: “What percentage of questions would I answer correctly on the entire AMBOSS Qbank for my study objective?"
Tracking EPC Changes
EPC updates continuously as you answer more questions. You may also see indicators showing how your EPC has changed over time (e.g., over the last 30 days), to help you track progress.
When is EPC Available?
EPC is unlocked once you have answered at least 40 questions for the selected study objective. This minimum is required to ensure the estimate is reliable. The more questions you answer, the more accurate your prediction will be.
Session-Level EPC Impact
After completing a question session, the Session Analysis page shows how that session affected your overall EPC (e.g., +0.5% EPC).
Why EPC Matters
Compared with raw percent correct, EPC:
- Reduces the influence of unusually easy or difficult question sets.
- Focuses on exam-relevant content.
- Needs fewer questions to become a good measure of performance.
Used consistently, EPC is a reliable indicator of your current level of mastery and exam preparedness. This helps you understand how each study session contributes to your overall exam readiness.
How was the EPC developed?
The EPC is based on principles from Item Response Theory (IRT). Educators and exam administrators have used IRT for decades to trace and measure student development.
The AMBOSS analytics system performs a real-time mapping of your performance on Qbank questions to a set of theta scores. These scores reflect your knowledge levels across medical topics.
To calculate the EPC for a given exam, the system converts these theta scores into probabilities of correctly answering all Qbank questions associated with that exam. The EPC is the average success rate across these questions.
Because of this approach, the EPC provides a better estimate of your current knowledge than the traditional percentage correct, which often lags behind your true level. The EPC also accounts for differences in question difficulty and topic importance (frequency).
We have validated the EPC system using real-world data from thousands of exam takers and continue to fine-tune it to improve its predictive accuracy.
Peer Group comparison
Peer Group Comparison shows how your performance compares with other learners who answered questions relevant to your current study objective.
What does the Peer Group Comparison show?
Your Peer Group Comparison displays your percentile rank relative to comparable AMBOSS learners. Your percentile indicates how many learners in your peer group you are currently outperforming.
Example: If you are in the 90th percentile, you performed better than 90% of learners on questions for your study objective, while 10% performed better than you.
Next to your percentile, you also see how your standing has changed over the last 30 days.
How is the percentile calculated?
Your percentile is based on your Equated Percent Correct (EPC) from questions completed within the last 12 months.
Your performance in your current study objective is compared with the performance of learners who have answered at least 40 relevant questions for that study objective in the past 12 months.
Additional calculation rules:
All question attempts are included.
Repeated attempts on the same question count each separately.
More recent answers are weighted more strongly through the EPC model.
How to interpret your percentile
Your percentile is a relative performance indicator, not a prediction of your exam score.
Keep in mind:
- Peer comparison does not account for exam date or study timeline.
- Some learners in your peer group may be closer to their exam or further along in preparation.
Performance over time
The performance over time chart shows how your key performance metrics have evolved over time. The metrics available depend on your study objective:
- Estimated exam score is available for USMLE Step 2 CK. The passing score threshold is also plotted for reference.
- Probability of passing is available for USMLE Step 1.
- EPC is available for all study objectives.
Expected score
The Expected Score estimates the score you would achieve if you took the exam today, based on your past performance in the Qbank. Currently, the Expected Score is available for the following study objective: USMLE Step 2.
To see an Expected Score, you must have answered at least 40 questions relevant to the study objective.
How the Expected Score is calculated
Your Expected Score is based on your Equated Percent correct (EPC) derived from your Qbank activity.
To calculate the estimate, the system considers:
- Your past Qbank performance
- Question difficulty
- Exam relevance of the questions
- Recency of your answers (more recent performance is weighted more strongly)
As you complete additional questions, the estimate becomes more precise and better reflects your current knowledge level.
Understanding the predicted score range
Your Expected Score is presented together with a predicted score range. This range indicates where your actual exam score is most likely to fall. Your real exam score is expected to fall within this range in 68% of cases.
The range becomes narrower as you answer more questions, because the system gains more data about your performance.
For example:
Expected Score: 256
Predicted Range: 246–265
This means that, based on your current performance, your most likely score is 256, and there is a 68% chance your score will fall between 246 and 265.
The Expected Score also shows how your predicted score has changed over the last 30 days.
Passing probability
The Expected Score also includes your Probability of Passing. This indicates the likelihood that you would pass the exam if you took it today, based on your Qbank performance.
Passing probability
The Passing Probability estimates the likelihood that you would pass the exam if you took it today, based on your past Qbank performance. It updates continuously as you answer more questions.
The passing probability is currently available for the following study objectives: USMLE Step 1, USMLE Step 2.
To see a Passing Probability estimate, you must have answered at least 40 questions relevant to the selected study objective.
Your Passing Probability represents the chance of passing the exam under similar conditions. For example, a 95% probability of passing means that if you were to take the exam 100 times, you would be expected to pass in about 95 cases.
As you answer more questions, the estimate becomes more reliable, because the system has more data to assess your performance.
The Passing Probability card also shows how your probability of passing has changed over the past 30 days.