For each of the following numerical valued random phenomena state conditions under which it may be expected to obey, either exactly or approximately, a Poisson probability law: (i) the number of telephone calls received at a given switchboard per minute; (ii) the number of automobiles passing a given point on a highway per minute; (iii) the number of bacterial colonies in a given culture per 0.01 square millimeter on a microscope slide; (iv) the number of times one receives 4 aces per 75 hands of bridge; (v) the number of defective screws per box of 100.