In a round-robin scheduling format, every team faces the other team in the tournament once. In some competitions (e.g., World Cup in soccer and cricket), the preliminary phase of the tournament will be conducted in a round-robin format, where members of a group play each other to determine which go through to the later elimination stage of the competition.
You can find here all the formats used in the ODI World Cups since the inaugural edition in 1975.
Application of the round-robin format
Round-robin formats are used in most of the major tournaments like World Cups in Cricket and Soccer. Usually, the league stages within these major tournaments are conducted in a round-robin format before the semi-final stages.
E.g., the 2019 Cricket World Cup took place in a round-robin format in England, where all ten teams faced the other teams once before they were ranked to qualify for the semi-finals. The top 4 teams – India, Australia, England, and New Zealand qualified for the semi-finals, from where the elimination rounds took place.
Advantages of the round-robin format
Round-robin format ideally called the fairest tournament format, as every team will be tested against every other possible opponent.
In a few round-robin tournaments, the format is used for deciding the champions without elimination rounds. That way, every team is given equal chances to come top.
With this format, not just the top four but all the participants in the tournament are ranked from top to bottom. So unlike the knock-out scheduling format, the round-robin ranks all participants in the tournament from the weakest to strongest performers.
Not just winning, round-robin will determine other factors like NRR, bonus points in the tournament, and head-to-head results, to provide more solutions in scenarios of tie-breakers.
Disadvantages of the round-robin format
Round-robins often lead to long tournaments, where the teams will be playing against one after another team.
Sometimes, too many games might bore the audience, especially if the teams are not competitive enough.
How to determine the number of games in a round-robin tournament?
The basic formula for calculating how many games a round-robin format conducts= n(n-1)/2, assuming n is the number of teams in the tournament.
E.g., the recent Cricket World Cup 2019 had ten teams in the tournament, which means n=10, and therefore,
The number of matches played in the league round before the semi-finals = 10(9)/2 = 45