Herman Wold facts for kids

Quick facts for kids Herman Wold
Born	(1908-12-25)25 December 1908 Skien, Norway
Died	16 February 1992(1992-02-16) (aged 83)
Nationality	Swedish
Alma mater	University of Stockholm
Known for	Wold's theorem MA() representation of stationary stochastic processes Wold decomposition (Operator theory) Cramér–Wold theorem Time series analysis Utility theory Consumer demand Latent variable Structural equation models Consistent least squares estimation of recursive triangular systems Causal inference in observational studies Partial least squares regression
Scientific career
Fields	Statistics Econometrics
Institutions	Uppsala University
Doctoral advisor	Harald Cramér
Doctoral students	Sten Malmquist Peter Whittle Karl Jöreskog

Herman Ole Andreas Wold (born December 25, 1908 – died February 16, 1992) was a smart person from Norway. He became a Swedish citizen and spent most of his career there. He was an econometrician and a statistician. This means he used math and statistics to study economics.

Wold was famous for his work in several areas. He studied how things change over time, which is called time series analysis. He also helped us understand how people make choices about buying things, known as consumer demand. His ideas also helped scientists figure out cause-and-effect relationships from data they collected.

Early Life and Moving to Sweden

Herman Wold was born in Skien, a town in Southern Norway. He was the youngest of six children in his family. In 1912, when Herman was four years old, his family moved to Sweden. They became Swedish citizens. Herman's father ran a small business that sold furs and hides.

Herman Wold's Scientific Discoveries

Herman Wold had a very long and successful career. He worked in science for more than 60 years!

Studying with Harald Cramér

In 1927, Herman Wold started studying mathematics at the University of Stockholm. This was a great time because a brilliant professor named Harald Cramér had just started teaching there. Cramér taught about math used in insurance and statistics. Wold later said it was "good luck" to be one of Cramér's first students.

After finishing his first degree in 1930, Wold worked for an insurance company. He also worked with Professor Cramér on information about how long people live. He even helped design new prices for insurance companies. Wold then started working on his PhD degree. His main teacher for this was Harald Cramér. While working on his PhD, Wold and Cramér also worked together on other projects. One of their most famous ideas was the Cramér–Wold theorem in 1936.

Understanding Time Series and the Wold Decomposition

Herman Wold's PhD paper was called A Study in the analysis of stationary time series. This paper was very important for understanding data that changes over time. Imagine you are tracking the temperature every day. That's a time series!

Wold's main discovery in this paper was the "Wold decomposition". This idea helps us break down a "stationary series" (data that has a constant average and spread over time) into two parts. One part is predictable, like the seasons changing every year. The other part is random, like sudden changes in weather. This discovery helped scientists better understand and predict patterns in all sorts of data, from weather to stock prices.

His work also brought together ideas from different scientists. It combined the work of English statisticians like Udny Yule with the ideas of Russian mathematicians like A. Ya. Khinchin. Later, Wold's student Peter Whittle expanded these ideas to more complex data sets.

Studying What People Buy

In 1938, the Swedish government asked Wold to study how people in Sweden spent their money. He published his findings in 1940. At the same time, he worked on the general idea of demand. His book Demand Analysis (1952) put all his ideas together. It covered how people decide what to buy, how to understand changing data, and how to use statistics to study these things.

Understanding Cause and Effect

Herman Wold also worked on how to figure out if one thing causes another. This is called causal inference. In the 1940s, other scientists were developing complex math models for this. Wold noticed some problems with their methods. He suggested a simpler way, especially for "observational studies". These are studies where scientists just watch and collect data, instead of doing experiments.

From 1945 to 1965, Wold developed his "recursive causal chain" model. He believed this model was better for many real-world situations. With his method, a simpler statistical tool called the least squares method worked very well. This method helped scientists understand cause-and-effect relationships more easily. Later, famous scientists like Judea Pearl recognized how important Wold's ideas on causality were.

Academic Career and Awards

Herman Wold had a successful career as a professor. In 1942, he became a professor of statistics at Uppsala University in Sweden. He stayed there until 1970. After that, he moved to Gothenburg and taught there until he retired in 1975.

In 1960, Wold became a member of the Royal Swedish Academy of Sciences. This is a very important group of scientists in Sweden. He was also part of the committee that chose the winners for the Sveriges Riksbank Prize in Economic Sciences in Memory of Alfred Nobel (often called the Nobel Prize in Economics) from 1968 to 1980.

See also

In Spanish: Herman Wold para niños