According to Chemical Engineering Progress, approximately 30% of all pipework failures in chemical plants are caused by operator error.

Suppose, for a particular plant, that out of a random sample of 20 pipework failures, exactly 5 are operational errors.Do you feel that the 30% figure stated above applies to this plant? Comment.

I did the math and

The book says that this answer means that the 30% figure is acceptable, but I don't understand why. I would have thought that the 30% figure would be acceptable if was close to 1. Can someone help me understand this? Thanks