Answer:
In the last step of the scientific process when they compare their results.
Step-by-step explanation:
The scientific process can be described of the following steps in order:
Starting with the observation, finding a point that asks a question which will be investigated, constructing a hypothesis that can be tested, testing the hypothesis and lastly comparing the results and starting over.
The example given in the question has a question to investigate, the students have a hypothesis. They test it and find out that the water sample can hold 20 amoeba which does not match their predictions. The students will check if their results match their predictions in the last step of the process when they compare their results with their hypothesis.
I hope this answer helps.