7.5. A survey was made of bicycle and other traffic in the neighbourhood of the Berkeley campus of the University of Califomia in 1993 (Gelman et al., 1995, p. 91). Sixty city streets were selected at random, with a stratification into three levels of activity and whether the street had a marked bicycle lane. The counts observed in one hour are shown in the table: for two of the streets the data were lost.