Similarly, you can also create variables to hold the values you want to test against. This helps you ensure consistent difficulty within a scene or chapter, lets you ramp up the difficulty over the course of the story, and makes it much easier (possible at all, really) to adjust the difficulty across the board if you find it needs tweaking once you start testing.
*create AWFUL 25
*create BAD 35
*create DECENT 50
*create GOOD 65
*create GREAT 75
*if stat < AWFUL
...
*if stat < BAD
...
*elseif stat < GOOD
...
*else
...
And so on.