=+13. Most car engines need at least 87 octane to avoid

“knocking” or “pinging,” terms used to describe the preignition that can happen when a fuel’s octane is too low.

An engineer is designing an experiment to raise the octane of an ethanol-based fuel. From previous studies, she thinks that with 8 experimental runs, she will have a power of 0.90 to detect a real increase of 3 points in the mean octane.