The latest attempt to guarantee a true college football national championship game was unveiled yesterday by the Bowl Championship Series, which concocted a complex formula of ratings that might have been devised by Stephen Hawking.

Had the system been in place last season, it would have guaranteed a matchup between Michigan and Nebraska, which were undefeated. Instead, Nebraska beat Tennessee to win the Orange Bowl and was voted national champion in the USA Today/ESPN coaches poll. Michigan won the Rose Bowl, which was not part of the bowl alliance format, and was voted No. 1 in the Associated Press poll.

The Bowl Championship Series is the new name for the Bowl Alliance, which was created to try to assure a true showdown for the No. 1 ranking. But only twice in six years did the alliance produce a national championship game, and the new system is an attempt to be sure that such a game takes place, beginning this season.

The new format creates a point system based on four factors:

*The average ranking of the A.P. and USA Today/ ESPN polls.

*A formula based on the average of the computer-generated rankings produced by The Seattle Times, Jeff Sagarin for USA Today and The New York Times.