Elzbieta Pleszczynska
Encyclopedia
Elżbieta Pleszczyńska is a Polish
full professor
of statistics
, activist of disability rights movement
.
, Faculty of Mathematics, Physics and Chemistry in 1956. She held position at Institute of Mathematics PAS until 1972. She received her Ph.D. in 1965 in the area of discriminant analysis ("Power of Test, and Separability of Hypothesis in Statistical Design of Experiments"). Her habilitation
thesis, titled "Trend Estimation Problems in Time Series Analysis", was accepted in 1973.
In 1967/8 she was visiting researcher in University of Wales
(Great Britain), and in 1971/2 in University of Montreal. In 1973 she moved to the Institute of Computer Science, PAS. In 1977, 1979 and 1989 she was awarded by the Polish Academy of Science. In 1981 she visited Italy
invited by CNR
. In the 1990s she started (together with her team) so called grade data analysis, a science of applying copula
and rank methods to problems of correspondence
and cluster analysis together with outlier
detection. (The adjective grade here honors statisticians of the first half of the 20th century, who called cumulative distribution function
s in this way.) In 1993 the President of the Republic of Poland
awarded Elżbieta Pleszczyńska with the Full Professor title in the area of mathematics. In 2000 she was an invited consultant of the Cambridge University.
In the Institute of Computer Science PAS, she had been leader of the Statistical Data Analysis division for many years. According to the Polish law, professors in PAS must retire at the age of 70. Retirement in 2003, although a bit confusing, didn't stop her scientific and social activity.
, like Pearson correlation coefficient, or least squares method produce comparable results only for comparable distribution types (in practice multivariate normal distribution is being assumed). Parametric statistical tests are derived from distribution assumptions. Classic methods fail if the input data contain strong outliers, and interpretation of their results should be different for different distribution types. In practice, the underlying assumptions are often not checked, moreover they are always violated – there is no normal distribution in the real world, because every real variable is limited (for example people cannot be –170 cm or +2 km tall), and the normal distribution implies positive probability density
for every real number
. In most cases the real distribution is skewed
or discrete, which doesn't prevent people from using normal distribution methods. The extend of this violation can be measured, but its maximum accepted level is just a convention, not mathematics. The parametric methods always work out of their conditions of use. However, their results are othen considered valid, which leads to "scientific" validation of false hypothesis. For the reasons mentioned above, Elżbieta Pleszczyńska is a strong advocate of explorative data analysis and non-parametric statistics
, like Spearman's rho
, Kendall's tau
, or grade data analysis.
(September 1990). For many years she has been the Foundation chairman.
The Foundation under her leadership is mainly interested in professional rehabilitation of physically disabled (not only mathematicians and specialists), based on computer techniques, like telework.
Pleszczyńska has been continuously focusing attention of the public opinion on rights of disable people, in her periodical reports.
district.
Poland
Poland , officially the Republic of Poland , is a country in Central Europe bordered by Germany to the west; the Czech Republic and Slovakia to the south; Ukraine, Belarus and Lithuania to the east; and the Baltic Sea and Kaliningrad Oblast, a Russian exclave, to the north...
full professor
Professor
A professor is a scholarly teacher; the precise meaning of the term varies by country. Literally, professor derives from Latin as a "person who professes" being usually an expert in arts or sciences; a teacher of high rank...
of statistics
Statistics
Statistics is the study of the collection, organization, analysis, and interpretation of data. It deals with all aspects of this, including the planning of data collection in terms of the design of surveys and experiments....
, activist of disability rights movement
Disability rights movement
The disability rights movement is the movement to secure equal opportunities and equal rights for people with disabilities. The specific goals and demands of the movement are: accessibility and safety in transportation, architecture, and the physical environment, equal opportunities in independent...
.
Biography
M.Sc in mathematics at University of WarsawUniversity of Warsaw
The University of Warsaw is the largest university in Poland and one of the most prestigious, ranked as best Polish university in 2010 and 2011...
, Faculty of Mathematics, Physics and Chemistry in 1956. She held position at Institute of Mathematics PAS until 1972. She received her Ph.D. in 1965 in the area of discriminant analysis ("Power of Test, and Separability of Hypothesis in Statistical Design of Experiments"). Her habilitation
Habilitation
Habilitation is the highest academic qualification a scholar can achieve by his or her own pursuit in several European and Asian countries. Earned after obtaining a research doctorate, such as a PhD, habilitation requires the candidate to write a professorial thesis based on independent...
thesis, titled "Trend Estimation Problems in Time Series Analysis", was accepted in 1973.
In 1967/8 she was visiting researcher in University of Wales
University of Wales
The University of Wales was a confederal university founded in 1893. It had accredited institutions throughout Wales, and formerly accredited courses in Britain and abroad, with over 100,000 students, but in October 2011, after a number of scandals, it withdrew all accreditation, and it was...
(Great Britain), and in 1971/2 in University of Montreal. In 1973 she moved to the Institute of Computer Science, PAS. In 1977, 1979 and 1989 she was awarded by the Polish Academy of Science. In 1981 she visited Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...
invited by CNR
Consiglio Nazionale delle Ricerche
The Consiglio Nazionale delle Ricerche or National Research Council, is an Italian public organization set up to support scientific and technological research. Its headquarters are in Rome.-History:The institution was founded in 1923...
. In the 1990s she started (together with her team) so called grade data analysis, a science of applying copula
Copula (statistics)
In probability theory and statistics, a copula can be used to describe the dependence between random variables. Copulas derive their name from linguistics....
and rank methods to problems of correspondence
Correspondence analysis
Correspondence analysis is a multivariate statistical technique proposed by Hirschfeld and later developed by Jean-Paul Benzécri. It is conceptually similar to principal component analysis, but applies to categorical rather than continuous data...
and cluster analysis together with outlier
Outlier
In statistics, an outlier is an observation that is numerically distant from the rest of the data. Grubbs defined an outlier as: An outlying observation, or outlier, is one that appears to deviate markedly from other members of the sample in which it occurs....
detection. (The adjective grade here honors statisticians of the first half of the 20th century, who called cumulative distribution function
Cumulative distribution function
In probability theory and statistics, the cumulative distribution function , or just distribution function, describes the probability that a real-valued random variable X with a given probability distribution will be found at a value less than or equal to x. Intuitively, it is the "area so far"...
s in this way.) In 1993 the President of the Republic of Poland
President of the Republic of Poland
The President of the Republic of Poland is the Polish head of state. His or her rights and obligations are determined in the Constitution of Poland....
awarded Elżbieta Pleszczyńska with the Full Professor title in the area of mathematics. In 2000 she was an invited consultant of the Cambridge University.
In the Institute of Computer Science PAS, she had been leader of the Statistical Data Analysis division for many years. According to the Polish law, professors in PAS must retire at the age of 70. Retirement in 2003, although a bit confusing, didn't stop her scientific and social activity.
Scientific views
Prof. Pleszczyńska is known for her criticism of the classic statistical approach. Classic parametric methodsParametric statistics
Parametric statistics is a branch of statistics that assumes that the data has come from a type of probability distribution and makes inferences about the parameters of the distribution. Most well-known elementary statistical methods are parametric....
, like Pearson correlation coefficient, or least squares method produce comparable results only for comparable distribution types (in practice multivariate normal distribution is being assumed). Parametric statistical tests are derived from distribution assumptions. Classic methods fail if the input data contain strong outliers, and interpretation of their results should be different for different distribution types. In practice, the underlying assumptions are often not checked, moreover they are always violated – there is no normal distribution in the real world, because every real variable is limited (for example people cannot be –170 cm or +2 km tall), and the normal distribution implies positive probability density
Probability density
Probability density may refer to:* Probability density function in probability theory* The product of the probability amplitude with its complex conjugate in quantum mechanics...
for every real number
Real number
In mathematics, a real number is a value that represents a quantity along a continuum, such as -5 , 4/3 , 8.6 , √2 and π...
. In most cases the real distribution is skewed
Skewness
In probability theory and statistics, skewness is a measure of the asymmetry of the probability distribution of a real-valued random variable. The skewness value can be positive or negative, or even undefined...
or discrete, which doesn't prevent people from using normal distribution methods. The extend of this violation can be measured, but its maximum accepted level is just a convention, not mathematics. The parametric methods always work out of their conditions of use. However, their results are othen considered valid, which leads to "scientific" validation of false hypothesis. For the reasons mentioned above, Elżbieta Pleszczyńska is a strong advocate of explorative data analysis and non-parametric statistics
Non-parametric statistics
In statistics, the term non-parametric statistics has at least two different meanings:The first meaning of non-parametric covers techniques that do not rely on data belonging to any particular distribution. These include, among others:...
, like Spearman's rho
Spearman's rank correlation coefficient
In statistics, Spearman's rank correlation coefficient or Spearman's rho, named after Charles Spearman and often denoted by the Greek letter \rho or as r_s, is a non-parametric measure of statistical dependence between two variables. It assesses how well the relationship between two variables can...
, Kendall's tau
Kendall tau rank correlation coefficient
In statistics, the Kendall rank correlation coefficient, commonly referred to as Kendall's tau coefficient, is a statistic used to measure the association between two measured quantities...
, or grade data analysis.
Social work
Elżbieta Pleszczyńska has cofounded Foundation Supporting Physically Disabled Mathematicians and Computer Specialists in WarsawWarsaw
Warsaw is the capital and largest city of Poland. It is located on the Vistula River, roughly from the Baltic Sea and from the Carpathian Mountains. Its population in 2010 was estimated at 1,716,855 residents with a greater metropolitan area of 2,631,902 residents, making Warsaw the 10th most...
(September 1990). For many years she has been the Foundation chairman.
The Foundation under her leadership is mainly interested in professional rehabilitation of physically disabled (not only mathematicians and specialists), based on computer techniques, like telework.
Pleszczyńska has been continuously focusing attention of the public opinion on rights of disable people, in her periodical reports.
Private life
She has a son – journalist – and two grandchildren. She lives in Warsaw WolaWola
Wola is a district in western Warsaw, Poland, formerly the village of Wielka Wola, incorporated into Warsaw in 1916. An industrial area with traditions reaching back to the early 19th century, it is slowly changing into an office and residential district...
district.