Legendary statistical scientist CR Rao dies

My first acquaintance with the man happened when I had joined ISI, Kolkata, as an undergraduate student in 1970. Mostly, everyday around 11 am, we would see from our classroom an unassuming man, often in chappals, walking down the hallway of the third floor of main building to enter the “tea room.” I learnt that many faculty members and research scholars assembled there to get guidance from him on mathematical or statistical problems. Most came out of the room smiling.

Rao studied mathematics at Andhra University and obtained a degree with top honours. Recognising his talent, his father encouraged him to study higher mathematics.

After his father’s death in 1941, Rao was called to Calcutta for an interview pertaining to his job application to the Indian military. A chance meeting with a person who knew of the ISI brought Rao to the Presidency College where Prasanta Chandra Mahalanobis had established ISI (before it was moved to its own campus). By speaking with some faculty members and workers, Rao felt that ISI was the right place for him.

In an interview in 2013, Rao stated: “I went back to Visakhapatnam and told my mother [that he would like] to get admitted to ISI for training in statistics, and it would cost me Rs 30 a month to stay in Kolkata. She said she would raise the money somehow and that I should go to Kolkata to join ISI. I travelled to Kolkata with `30 in my pocket and joined ISI on 1 January 1941.”

Rao’s seminal contributions have been in areas of statistics that deal with designing an experiment for efficient extraction of information and testing scientific hypothesis using the results of the experiment.

After he had obtained his MA, Rao was offered a technical apprenticeship in ISI. He also began to teach statistics at Calcutta University. In 1944, he derived a seminal result with which his name is associated — the Cramer-Rao bound. In 1945, he proved a result that is now known as the Rao-Blackwell theorem.

Often, we need to obtain knowledge of an unknown feature of a population like, say, the average monthly income of an Indian. Data can be collected only from a small number of people. From these data, one can obtain an approximate knowledge of monthly income. There are several ways of obtaining estimates from data, but the method proposed by Rao, and two years later by David Blackwell, results in highly reliable estimates.

He went to Cambridge and obtained a PhD under Ronald Fisher, a founder of modern statistical science. During his PhD, he discovered a method, now known as Rao’s Score Test, which is used in all branches of science.

Rao returned to India in 1948 and became a professor in ISI at 28; in 1964, he was appointed its Director. After his retirement from ISI, he moved to the US. In 1982, he established the Center of Multivariate Analysis at the University of Pittsburgh. He joined the Pennsylvania State University in 1988. In 2007, the University of Hyderabad opened the C R Rao Advanced Institute of Mathematics, Statistics and Computer Science. Around 2010, Rao moved to the University of Buffalo at Amherst. He published his last scientific work in his 100th year.

Rao was hugely creative. He used to categorise creativity in two kinds.

“At its highest level, it is the birth of a new idea or a theory which is qualitatively different from and not conforming to or deducible from any existing paradigm, and which explains a wider set of natural phenomena than any existing theory. There is creativity of another kind at a different level, of a discovery made within the framework of an existing paradigm but of immense significance in a particular discipline.”

Rao had excelled in creativity of both kinds.

Partha P Majumder is one of India’s leading biostatisticians and is currently at ISI, Kolkata