Douglas Hubbard mentions a few rules of the sort you seem to be describing in his book How to measure anything. For example, his “Rule of Five” states that «There is a 93.75% chance that the median of a population is between the smallest and largest values in any random sample of five from that population.» One of the central themes in that book is in fact that you “have more data that you think”, and that these simple rules can take you surprisingly far.
Douglas Hubbard mentions a few rules of the sort you seem to be describing in his book How to measure anything. For example, his “Rule of Five” states that «There is a 93.75% chance that the median of a population is between the smallest and largest values in any random sample of five from that population.» One of the central themes in that book is in fact that you “have more data that you think”, and that these simple rules can take you surprisingly far.