Your TOEFL scores may decrease, remain the same, or increase. ETS does not take your previous scores into account. Even though TOEFL is a standardized test, topics, vocabulary, and expressions vary from test to test. This is where the element of luck comes in. If you take the test and you are familiar with the reading topics, and let's say, there is only vocabulary that you know, you will of course do better than on another test that uses a topic that you are completely unfamiliar with and that contains vocabulary that you have never seen before. This is why you need to practice and prepare for a really wide range of topics and vocabulary. Moreover, do not forget the human element. You are not a robot! You can have a good day or a bad day, which does in fact influence your concentration and performance. After all, this is not just a language test, it is an endurance test. They want to see how well you can perform a number of tasks in English under time pressure. Consequently, you will do better on some days and worse on other days. We need to take all that into consideration.
