  In this paper, we examine team ball sports to investigate how the likelihood
of weaker teams winning against stronger ones, referred to as underdog
achievement, is influenced by inherent randomness factors that affect match
outcomes in such sports. To address our research question, we collected data on
match scores and computed corresponding team rankings from major international
competitions for 12 popular team ball sports: basketball, cricket, field
hockey, futsal, handball, ice hockey, lacrosse, roller hockey, rugby, soccer,
volleyball, and water polo. Then, we developed an underdog achievement score to
identify the sports with the highest occurrences of weaker teams prevailing
over stronger ones, and we designed a randomness model consisting of factors
that contribute to unexpected match outcomes within each sport. Our findings
indicate that soccer is among the sports in which a weaker team is most likely
to win. Through principal component analysis (PCA) and correlation analysis, we
demonstrate that our randomness model can explain such a phenomenon, showing
that the underdog achievement can be attributed to numerous factors that can
randomly influence match outcomes.
