Final answer:
Treating 'Some A's are not B' as equivalent to 'Some B's are not A' commits a conversion error, which is a logical fallacy. It shows a bias in reasoning and leads to incorrect conclusions.
Step-by-step explanation:
When people treat "Some A's are not B" as equivalent to "Some B's are not A," they are committing a logical fallacy known as a conversion error. This error occurs when someone incorrectly assumes that two statements are logically equivalent when they are not. An example of this can be seen with probabilities regarding beliefs and safety concerning rock climbing equipment or in the misunderstanding of statistical errors such as Type I and Type II errors. The bias towards believing these kinds of statements as equivalent can lead to flawed reasoning and incorrect conclusions.