In 1984, Eric Dickerson broke the reco zoom in rushing yards in a season (2105 yards) that had been held by O.J. Simpson since 1973 (2003 yards). However, there were many differences between football in 1984 and football in 1973, including the number of teams and number of games played. The mean number of yards for the top 52 running backs in 1973 was 703 yards with a standard deviation of 292 yards. The mean number of yards for the top 56 running backs in 1984 was 737 yards with a standard deviation of 383 yards. Find Simpson's z-score. Round z-score to 2 decimal places