P.C. Mahalanobis was born in Calcutta (now Kolkata) to Prabodh Chandra and Nirodbashini Devi. He was the eldest of two brothers and three sisters. Mahalanobis received his early schooling at the Brahmo Boys School in Kolkata. During his early age, Mahalanobis came under the influence of Rabindranath Tagore. Tagore was impressed by his love of literature with a flair for logical analysis. Mahalanobis joined the Presidency College, Kolkata, and graduated with a BSc with honours in physics in 1912. Jagadis Chandra Bose and Prafulla Chandra Ray were among the teachers who taught Mahalanobis in Presidency College. MeghnadSaha was a year junior and Subhas Chandra Bose was two years his junior in college.
Mahalanobis went to England in 1913 with an intention to study at the University of London. He took admission for a BSc course. The course was to begin in a few weeks time. During this time he made a trip to Cambridge and visited King’s College. Mahalanobis was overwhelmed by the architectural beauty of the chapel of King’s College. He missed the train back to London and stayed the night with a friend. In the friend’s house, he met a student who was studying at King’s College. On hearing that Mahalanobis found the chapel so attractive, the friend suggested he could apply to study there. Interestingly, he was interviewed the next day and given admission at the King’s College. Mahalanobis passed Part I of the Mathematical Tripos in 1914 and Natural Sciences Tripos in 1915. He obtained a first class pass in Part II and was awarded a Senior Scholarship by King’s College. During his time in Cambridge, he interacted with Srinivasa Ramanujan.
Mahalanobis wanted to do research in physics and started working with Scottish physicist and meteorologist C.T.R. Wilson (1869–1959) at the Cavendish Laboratory. In July 1915, Mahalanobis visited India for a short holiday, but never returned to England. Before his journey to India, he came across a few volumes of Biometrika, a peer-reviewed scientific journal with principal focus on theoretical statistics. Mahalanobis found the papers so interesting that he purchased the whole set of available volumes and brought these back to Kolkata. A window was opened for Mahalanobis to a new area of science, permanently changing the direction of his life. Mahalanobis realised that statistics was a new science connected with measurements and their analysis, and as such capable of modelling a wide range of applications. Before Mahalanobis, statistics was almost unknown in India and the subject was not taught in any Indian University. He brought about profound changes which influenced the future development of statistics in India.
Once back in India, his uncle, Subodh Chandra Mahalanobis, a professor of physiology at Presidency College, introduced him to the Principal of the College. It was the time of World War I and the senior physicist of Presidency College was on war duty. Mahalanobis was offered a temporary teaching job at Presidency College, which he accepted. He soon became so involved with his work in the College that he gave up the idea of returning to Cambridge. Mahalanobis first analysed the examination results of Presidency College using statistical tools. He discovered the utility of statistics to problems in meteorology, anthropology and began working on it. During this time Mahalanobis met Nelson Annadale, the then Director of Zoological and Anthropological Survey of India, who had collected anthropometric measurements on Anglo-Indians of Kolkata.
Annadale requested Mahalanobis to analyse the data. Mahalanobis was influenced by the anthropometric studies published in the journal Biometrikaand readily accepted to do statistical analysis. During the course of these studies, he found a way of comparing and grouping populations using a multivariate distance measure. This measure denoted “D2” and now eponymously named ‘Mahalanobis distance’, is independent of the measurement scale. Based on the statistical analysis, Mahalanobis wrote his first paper in 1922 entitled ‘Anthropological Observations on Anglo-Indians of Calcutta, Part I: Male Stature’. This paper attracted the attention of Sir Gilbert Walker, Director General of Observatories, who requested Mahalanobis to undertake a systematic study of some meteorological problems. While working on this, Mahalanobis discovered that the region of highest control for changes in weather on the surface of the Earth is located about 4 kilometres above the sea-level, a result, which was rediscovered several years later by Franz Bauer in Germany from physical consideration. Subsequently, he took up responsibility as a meteorologist in the Alipore Observatory in Kolkata in addition to his duty as professor of physics at the Presidency College.
The most important contribution of Mahalanobis is large- scale sample surveys. He introduced the concept of pilot surveys and advocated the usefulness of sampling methods. Mahalanobis designed statistical tools to analyse agriculture yield. He introduced a method for estimating crop yields, which involved statisticians sampling in the fields by cutting crops in a circle of diameter 4 feet (about 1.22 metres). Mahalanobis extended the method of sampling survey to analyse consumer expenditure, tea-drinking habits, public opinion, crop acreage and plant diseases. Famous mathematical statistician and economic theorist Harold Hotelling wrote: “No technique of random sample has, so far as I can find, been developed in the United States or elsewhere, which can compare in accuracy with that described by Professor Mahalanobis”.
Perhaps the most important contribution byMahalanobis, other than his scientific papers, was setting up the Indian Statistical Institute. During 1920,while working as a part-time teacher in PresidencyCollege, Mahalanobis started his research on statistics.Many of his colleagues also joined him and started doingresearch. Soon it acquired the name of the StatisticalLaboratory and was located in Mahalanobis’s room inthe Physics Department. The official setting up of Indian Statistical Institute came after a decade, with tireless effort of Mahalanobis. During this period, almost all statistical works done in India were by Mahalanobis. Finally, the Indian Statistical Institute was formally founded on 17 December 1931. As the Director and Secretary of the Institute, Mahalanobis persuaded many bright young physicists and mathematicians to join the Institute. They included Raj Chandra Bose, Samarendra Nath Roy, and C.R. Rao. In 1959, by an act of the Indian Parliament, the Institute was declared as an “Institution of National Importance”.
The renowned mathematician and statistician C.R. Rao, student of P.C. Mahalanobis, described him as “mentally alert and physically active throughout his life” in his memoir. He wrote, “Even after he was admitted to the nursing home in Calcutta (now Kolkata), he was constantly thinking of the new statistical tool he was developing.”
The English statistician Sir Ronal Fisher once commented about Professor Mahalanobis’ works in the following words: “What at first most strongly attracted my admiration was that the Professor’s work was not imitative…it is the work of striking originality. These words reflect the outstanding contributions of Mahalanobis to statistics. It is therefore not surprising that his works are the backbone of several application areas of modern statistical sciences. Apart from his academic excellence, he made an untiring effort to expand the knowledge of statistics in India and applied the technological innovations for the welfare of people. The originality of ideas coupled with a zeal and conviction to implement new ideas was the hallmark of Mahalanobis’ personality”.