This Real Life Adventures comic makes my exact point today:
In high school I read a book titled How to Lie with Statistics, and this was one of its points. Here’s the rule:
When you mention a comparison, say what you’re comparing to!
If someone says, for example, “My product is better!” Ask: Better than the competition? Better than it used to be? Better than the worst similar product? Better than the reviewers say it is? Better than a first grader could do?
The point of expository writing is to explain things, so don’t leave your reader guessing.