What does the status evaluation "5 by 5" mean?

It's a term used by the pilot in Aliens right before the small landing craft is launched from the interstellar mother ship (in the 2nd Alien movie). It's also a term used in Buffy the Vampire Slayer - the Faith character uses it a lot, but no one else knows what it means.

I've found the answer to this one! It is a way of describing the quality of sound in communications. The first number is for the strength of the signal, and the second number is the clarity of the signal. 5 is the best rating for each, so it means "excellent strength and perfect clarity".

The question then becomes, does that have anything to do with the movie or the TV show?

No one is left on the interstellar mother ship in Aliens to communicate with the people in the landing craft, everyone is in the same ship. They could turn around and talk to each other in person. The landing ship does drop off a big tank with most of the people in it and then flies away from them, but they were not testing the communications between the two of those vehicles.

There is no testing of any equipment for sound or other abilities on Buffy the Vampire Slayer. I think the Faith character was just quoting from the Aliens movie because "5 by 5" sounds cool.

I think the Aliens movie uses "5 by 5" just because it sounds cool too.

Pondering questions of "what does that mean" can be fun, but don't expect deeply philosophical answers.