 In the field of statistics and applied probability , John Graunt published Natural and Political Observations Made upon the Bills of Mortality also in 1662 , initiating the discipline of demography . This work , among other things , gave a statistical estimate of the population of London , produced the first life table , gave probabilities of survival of different age groups , examined the different causes of death , noting that the annual rate of suicide and accident is constant , and commented on the level and stability of sex ratio . The usefulness and interpretation of Graunt 's tables were discussed in a series of correspondences by brothers Ludwig and Christiaan Huygens in 1667 , where they realized the difference between mean and median estimates and Christian even interpolated Graunt 's life table by a smooth curve , creating the first continuous probability distribution ; but their correspondences were not published . Later , Johan de Witt , the then prime minister of the Dutch Republic , published similar material in his 1671 work <unk> van <unk> @-@ <unk> ( A Treatise on Life <unk> ) , which used statistical concepts to determine life expectancy for practical political purposes ; a demonstration of the fact that this sapling branch of mathematics had significant pragmatic applications . De Witt 's work was not widely distributed beyond the Dutch Republic , perhaps due to his fall from power and execution by mob in 1672 . Apart from the practical contributions of these two work , they also exposed a fundamental idea that probability can be assigned to events that do not have inherent physical symmetry , such as the chances of dying at certain age , unlike say the rolling of a dice or flipping of a coin , simply by counting the frequency of occurrence . Thus probability could be more than mere combinatorics . 
