• Bias;
  • Clustering;
  • Random number generators;
  • Singletons

The paper describes an investigation in which four groups of university students, of sizes 228, 111, 51 and 68, were asked to generate randomly a sequence of 25 digits from {0, 1, 2, 3, 4, 5, 6, 7, 8, 9}. Previous studies of this kind have suggested that people have tendencies to avoid repetition, to respond serially and to cycle. The aim of our investigation was to study further the nature and extent of people's biases. Particular emphasis was put on the frequency and spread of digits in a selection, as well as on aspects of repetition and clustering. The distribution of the number of clusters of size k was obtained, and our analysis includes the use of this distribution. Our results support previous research showing the very special (and less favoured) status of 0 but also show a strong tendency of students to balance selections and to avoid clustering and sequentially repeating digits.