Levene enrolled at Columbia University and in his spare time conducted biochemical research, publishing papers on the chemical structure of sugars. In 1896 he was appointed as an Associate in the Pathological Institute of the New York State Hospitals, but he had to take time off to recuperate from tuberculosis.
This graph shows the median age of the resident population of the United States from 1960 to 2015. In 2015, the median age of the United States population was approximately 37.7 years.
It doesn't make any difference if there are 100 people in the group and 90% are over 50. The median age is still 50. The average age is computed by adding up all the ages of the 100 people and dividing that total by 100. If 90% of the people are over 50, the average could be 65 or more.