One of the most common questions I get as a USMLE tutor is:
"What is the difference between the NBME Comprehensive Basic Science Self Assessments (often referred to as just NBMEs) and the UWorld Self Assessments (UWSAs)?"
For starters, the NBME and UWSA are both practice tests that students take to help them prepare for the USMLE Step 1 exam, to gauge their study progress, and to predict their final score.
There are six NBMEs that are available for purchase for $60 each (and in 2020 an additional five that are available for free). There are two UWSAs that are included in your UWorld subscription if you buy at least a 180 day subscription.
NBMEs consist of four sections of 50 questions while the UWSAs contain four sections of 40 questions. The actual USMLE Step 1 exam is made up of 7 blocks of a maximum of 40 questions per block.
NBME and UWSA: Varying Question Styles
Aside from the obvious differences mentioned above, the NBMEs and UWSAs vary in their question styles. NBME questions tend to be much shorter in length and more vague than the UWSAs.
The USMLE Step 1 exam tends to resemble NBME style questions more closely, but in my experience the UWSAs often better predict final exam scores than the NBMEs for many students.
Recommendation: start with NBMEs and save the two UWSA for the final few weeks of studying.
The NBME-style of questions can take a little bit of time getting used to for some students. For this reason, many students see bigger variations between their NBME scores on different NBME forms when compared to their UWSA scores.
The UWSAs consist of UWorld-style questions and are therefore more familiar to students. Of course, there are many factors that contribute to variations in scores (i.e. anxiety levels that day, whether the test taker is well rested or not, the physical setting of the practice test, where you are in your study period) that also contribute to these fluctuations.
Since neither one of these practice tests mimic the entire length of the Step 1 USMLE exam, some students choose to take 3 timed UWorld question blocks following a UWSA or NBME to better simulate the actual exam length. I generally recommend doing this once or twice towards the very end of your designated study period to practice the timing of your breaks. This way you can ensure that your breaks are scheduled out in a way that will work best for when you sit for the actual exam.
Our tutors at Med School Tutors recommend taking as many practice tests as possible including both UWSAs. When to take each practice test varies by tutor and individual, but ultimately the more practice tests you do, the more equipped you will be to tackle the USMLE Step 1 when the day comes.