Retired professional tennis players Martina Navratilova, Monica Seles, John McEnroe, and Jimmy Connors are all left-handed. Define the parameter of interest to be the proportion of all professional tennis players (current and retired) who are left-handed. Only 20% of the general population is left-handed, but researchers believe this percent is higher in the population of all professional tennis players. In a survey of 47 professional tennis players, seven are left-handed.