John Wilder Tukey was an American mathematician best known for development of the FFT algorithm and box plot. The Tukey range test, the Tukey lambda distribution, the Tukey test of additivity, the Teichmüller–Tukey lemma all bear his name, he is credited with coining the term'bit'. Tukey was born in New Bedford, Massachusetts, in 1915, obtained a B. A. in 1936 and M. Sc. in 1937, in chemistry, from Brown University, before moving to Princeton University where he received a Ph. D. in mathematics. During World War II, Tukey worked at the Fire Control Research Office and collaborated with Samuel Wilks and William Cochran. After the war, he returned to Princeton, dividing his time between the university and AT&T Bell Laboratories, he became a full professor at 35 and founding chairman of the Princeton statistics department in 1965. Among many contributions to civil society, Tukey served on a committee of the American Statistical Association that produced a report challenging the conclusions of the Kinsey Report, Statistical Problems of the Kinsey Report on Sexual Behavior in the Human Male.
He was awarded the National Medal of Science by President Nixon in 1973. He was awarded the IEEE Medal of Honor in 1982 "For his contributions to the spectral analysis of random processes and the fast Fourier transform algorithm." Tukey retired in 1985. He died in New Brunswick, New Jersey, on July 26, 2000. Early in his career Tukey worked on developing statistical methods for computers at Bell Labs where he invented the term "bit", his statistical interests were many and varied. He is remembered for his development with James Cooley of the Cooley–Tukey FFT algorithm. In 1970, he contributed to what is today known as the jackknife estimation—also termed Quenouille–Tukey jackknife, he introduced the box plot in his 1977 book, "Exploratory Data Analysis." Tukey's range test, the Tukey lambda distribution, Tukey's test of additivity, Tukey's lemma, the Tukey window all bear his name. He is the creator of several little-known methods such as the trimean and median-median line, an easier alternative to linear regression.
In 1974, he developed, with the concept of the projection pursuit. He contributed to statistical practice and articulated the important distinction between exploratory data analysis and confirmatory data analysis, believing that much statistical methodology placed too great an emphasis on the latter. Though he believed in the utility of separating the two types of analysis, he pointed out that sometimes in natural science, this was problematic and termed such situations uncomfortable science. A. D. Gordon offered the following summary of Tukey's principles for statistical practice:... the usefulness and limitation of mathematical statistics. Tukey coined many statistical terms that have become part of common usage, but the two most famous coinages attributed to him were related to computer science. While working with John von Neumann on early computer designs, Tukey introduced the word "bit" as a contraction of "binary digit"; the term "bit" was first used in an article by Claude Shannon in 1948.
In 2000, Fred Shapiro, a librarian at the Yale Law School, published a letter revealing that Tukey's 1958 paper "The Teaching of Concrete Mathematics" contained the earliest known usage of the term "software" found in a search of JSTOR's electronic archives, predating the OED's citation by two years. This led many to credit Tukey with coining the term in obituaries published that same year, although Tukey never claimed credit for any such coinage. In 1995, Paul Niquette claimed he had coined the term in October 1953, although he could not find any documents supporting his claim; the earliest known publication of the term "software" in an engineering context was in August 1953 by Richard R. Carhart, in a Rand Corporation Research Memorandum. List of pioneers in computer science Andrews, David F. Robust estimates of location: survey and advances. Princeton University Press. ISBN 978-0-691-08113-7. OCLC 369963. Basford, Kaye E. Graphical analysis of multiresponse data. Chapman & Hall/CRC. ISBN 978-0-8493-0384-5.
OCLC 154674707. Blackman, R B; the measurement of power spectra from the point of view of communications engineering. Dover Publications. ISBN 978-0-486-60507-4. Cochran, William G. Statistical problems of the Kinsey report on sexual behavior in the human male. Journal of the American Statistical Association. Hoaglin, David C. Understanding Robust and Exploratory Data Analysis. Wiley. ISBN 978-0-471-09777-8. OCLC 8495063. CS1 maint: Multiple names: authors list CS1 maint: Extra text: authors list Hoaglin, David C. Exploring Data Tables and Shapes. Wiley. ISBN 978-0-471-09776-1. OCLC 11550398. CS1 maint: Multiple names: authors list CS1 maint: Extra text: authors list Hoagl
YouTube is an American video-sharing website headquartered in San Bruno, California. Three former PayPal employees—Chad Hurley, Steve Chen, Jawed Karim—created the service in February 2005. Google bought the site in November 2006 for US$1.65 billion. YouTube allows users to upload, rate, add to playlists, comment on videos, subscribe to other users, it offers a wide variety of corporate media videos. Available content includes video clips, TV show clips, music videos and documentary films, audio recordings, movie trailers, live streams, other content such as video blogging, short original videos, educational videos. Most of the content on YouTube is uploaded by individuals, but media corporations including CBS, the BBC, Hulu offer some of their material via YouTube as part of the YouTube partnership program. Unregistered users can only watch videos on the site, while registered users are permitted to upload an unlimited number of videos and add comments to videos. Videos deemed inappropriate are available only to registered users affirming themselves to be at least 18 years old.
YouTube and its creators earn advertising revenue from Google AdSense, a program which targets ads according to site content and audience. The vast majority of its videos are free to view, but there are exceptions, including subscription-based premium channels, film rentals, as well as YouTube Music and YouTube Premium, subscription services offering premium and ad-free music streaming, ad-free access to all content, including exclusive content commissioned from notable personalities; as of February 2017, there were more than 400 hours of content uploaded to YouTube each minute, one billion hours of content being watched on YouTube every day. As of August 2018, the website is ranked as the second-most popular site in the world, according to Alexa Internet. YouTube has faced criticism over aspects of its operations, including its handling of copyrighted content contained within uploaded videos, its recommendation algorithms perpetuating videos that promote conspiracy theories and falsehoods, hosting videos ostensibly targeting children but containing violent and/or sexually suggestive content involving popular characters, videos of minors attracting pedophilic activities in their comment sections, fluctuating policies on the types of content, eligible to be monetized with advertising.
YouTube was founded by Chad Hurley, Steve Chen, Jawed Karim, who were all early employees of PayPal. Hurley had studied design at Indiana University of Pennsylvania, Chen and Karim studied computer science together at the University of Illinois at Urbana–Champaign. According to a story, repeated in the media and Chen developed the idea for YouTube during the early months of 2005, after they had experienced difficulty sharing videos, shot at a dinner party at Chen's apartment in San Francisco. Karim did not attend the party and denied that it had occurred, but Chen commented that the idea that YouTube was founded after a dinner party "was very strengthened by marketing ideas around creating a story, digestible". Karim said the inspiration for YouTube first came from Janet Jackson's role in the 2004 Super Bowl incident, when her breast was exposed during her performance, from the 2004 Indian Ocean tsunami. Karim could not find video clips of either event online, which led to the idea of a video sharing site.
Hurley and Chen said that the original idea for YouTube was a video version of an online dating service, had been influenced by the website Hot or Not. Difficulty in finding enough dating videos led to a change of plans, with the site's founders deciding to accept uploads of any type of video. YouTube began as a venture capital-funded technology startup from an $11.5 million investment by Sequoia Capital and an $8 million investment from Artis Capital Management between November 2005 and April 2006. YouTube's early headquarters were situated above a pizzeria and Japanese restaurant in San Mateo, California; the domain name www.youtube.com was activated on February 14, 2005, the website was developed over the subsequent months. The first YouTube video, titled Me at the zoo, shows co-founder Jawed Karim at the San Diego Zoo; the video was uploaded on April 23, 2005, can still be viewed on the site. YouTube offered the public a beta test of the site in May 2005; the first video to reach one million views was a Nike advertisement featuring Ronaldinho in November 2005.
Following a $3.5 million investment from Sequoia Capital in November, the site launched on December 15, 2005, by which time the site was receiving 8 million views a day. The site grew and, in July 2006, the company announced that more than 65,000 new videos were being uploaded every day, that the site was receiving 100 million video views per day. According to data published by market research company comScore, YouTube is the dominant provider of online video in the United States, with a market share of around 43% and more than 14 billion views of videos in May 2010. In May 2011, 48 hours of new videos were uploaded to the site every minute, which increased to 60 hours every minute in January 2012, 100 hours every minute in May 2013, 300 hours every minute in November 2014, 400 hours every minute in February 2017; as of January 2012, the site had 800 million unique users a month. It is estimated that in 2007 YouTube consumed as much bandwidth as the entire Internet in 2000. According to third-party web analytics providers and SimilarWeb, YouTube is the second-most visited website in the world, as of December 2016.
Major Greenwood FRS was an English epidemiologist and statistician. Major Greenwood junior was born in Shoreditch in London's East End, the only child of Major Greenwood, a doctor in general practice there and his wife Annie, daughter of Peter Lodwick Burchell, F. R. C. S. M. B. L. S. A; the Greenwood family is recorded back to the twelfth century in the person of Wyomarus Greenwode, of Greenwode Leghe, near Heptonstall, caterer to the Empress Maude in 1154. Greenwood was educated on the classical side at Merchant Taylors' School and went on to study medicine at University College London and the London Hospital. On qualifying in 1904 he worked for a time as assistant to his father but after a few months he gave up clinical practice for good, he went to work as a demonstrator for the physiologist Leonard Hill at the London Hospital Medical College. Leonard Hill recalled, "By recognising the ability of a student with nothing behind him to show his worth and by appointing him my assistant I may claim to have started Greenwood on his career."
While Greenwood made a good start in physiological research he was drawn to statistics. After a period of study with Karl Pearson he was appointed statistician to the Lister Institute in 1910. There he worked on a wide range of problems, including a study of the effectiveness of inoculation with the statistician Udny Yule. In the First World War Greenwood first served in the Royal Army Medical Corps but was put in charge of a medical research unit at the Ministry of Munitions. There he investigated the health problems associated with factory work, one result of, an influential study of accidents which he produced with Yule. In 1919 Greenwood joined the newly created Ministry of Health with responsibility for medical statistics, he co-authored a number of papers with Ethel Newbold during his tenure there. In 1928 he became the first professor of Epidemiology and Vital Statistics at the London School of Hygiene and Tropical Medicine where he stayed until he retired in 1945, he established a group of researchers.
Greenwood played the same role in A. B. Hill's career; the Royal Society awarded the Buchanan Medal to Greenwood in 1927, elected him a Fellow in 1928. The election certificate stated Engaged in medical research. Has applied the statistical method to the elucidation of many problems of physiology, pathology and epidemiology. Is the author, or joint author, of more than sixty papers dealing with these applications, including important contributions to the experimental study of epidemiology. Has done much to encourage and develop the use of modern statistical methods by medical laboratory investigators, and, as Chairman of the Medical Research Council's Statistical Committee, to secure the adequate planning and execution of field investigations, he was elected President of the Royal Statistical Society in 1934 and awarded its Guy Medal in Gold in 1945. Greenwood produced a large body of research, was the first holder of important positions in modern medical statistics and wrote extensively on the history of his subject, but as Austin Bradford Hill wrote in his obituary, "in the future, it may well indeed seem that one of his greatest contributions, if not the greatest, lay in his outlook, in his statistical approach to medicine a new approach and one long regarded with suspicion.
And he fought this fight continuously and honestly—for logic for accuracy, for ‘little sums.’" His name is attached to the Greenwood formula for the variance or standard error of the Kaplan–Meier estimator of survival. A statistical method invented by Major Greenwood in a statistical study of infectious diseases is still used in present-day research; the Greenwood statistic was used to discover that there is some kind of order in the placement of genes on the chromosomes of living things and this inspired a new look at epigenetics, now considered to be as important as genetics in how living organisms develop and evolve. Greenwood lived at Loughton, where among his neighbours were Sir Frank Baines, Millais Culpin, Leonard Erskine Hill. Greenwood, M.. "A First Study of the Weight and Correlation of the Human Viscera, with Special Reference to the Healthy and Diseased Heart". Biometrika. 3: 63–83. Doi:10.1093/biomet/3.1.63. Greenwood, M.. Physiology of the special senses. London: E. Arnold. Greenwood, M.
"The Statistics of Anti-typhoid and Anti-cholera Inoculations, the Interpretation of such Statistics in general". Proceedings of the Royal Society of Medicine. 8: 113–94. PMC 2004181. PMID 19978918. Greenwood, Major & Udny Yule, G.. "An Inquiry into the Nature of Frequency Distributions Representative of Multiple Happenings with Particular Reference to the Occurrence of Multiple Attacks of Disease or of Repeated Accidents". Journal of the Royal Statistical Society. 83: 255–279. Doi:10.2307/2341080. JSTOR 2341080.\ Edgar L. Collis and Major Greenwood; the health of the industrial worker. 1921 Cripps, L, Greenwood, M. and Newbold, E. "A Biometric Study of the Inter-relations of `Vital Capacity' stature, stem length and weight in a Sample of Healthy Male Adults". Biometrika. 14: 3–4. Doi:10.2307/2331816. JSTOR 2331816. Greenwood, M.. "On the Estimation of Metabolism from Determination of Carbon Dioxyde Production and on Estimation of External W
A frugivore is an animal that thrives on raw fruits, succulent fruit-like vegetables, shoots and seeds. It can be any type of omnivore where fruit is a preferred food type; because 20% of all mammalian herbivores eat fruit, frugivory is common among mammals. Since frugivores eat a lot of fruit, they are dependent on the abundance and nutritional composition of fruits. Frugivores can either benefit fruit-producing plants by dispersing seeds, or they can hinder plants by digesting seeds along with the fruits; when both the fruit-producing plant and the frugivore species benefit by fruit-eating behavior, their interaction is called mutualism. Seed dispersal is important for plants because it allows their progeny to move away from their parents over time; the advantages of seed dispersal may have led to the evolution of fleshy fruits, which entice animals to eat the fruits and move the plants seeds from place to place. While many fruit-producing plant species would not disperse far without frugivores, they can germinate if they fall to the ground directly below the parent plant.
Many types of animals are seed dispersers. Mammal and bird species represent the majority of seed-dispersing species. However, frugivorous tortoises, lizards and fish disperse seeds. For example, cassowaries are a keystone species because they spread fruit through digestion, many seeds will not grow unless they have been digested by a cassowary. While frugivores and fruit-producing plant species are present worldwide, there is some evidence that tropical forests have more frugivore seed dispersers than the temperate zone. Frugivore seed dispersal is a common phenomenon in many ecosystems. However, it is not a specific type of plant–animal interaction. For example, a single species of frugivorous bird may disperse fruits from several species of plants, or a few species of bird may disperse seeds of one plant species; this lack of specialization could be because fruit availability varies by season and year, which tends to discourage frugivore animals from focusing on just one plant species. Furthermore, different seed dispersers tend to disperse seeds to different habitats, at different abundances, distances, depending on their behavior and numbers.
There are a number of fruit characteristics that seem to be adaptive characteristics to attract frugivores. Many animal-dispersed fruits advertise their palatability to animals with bright colors and attractive smells. Fruit pulp is rich in water and carbohydrates and low in protein and lipids. However, the exact nutritional composition of fruits varies widely; the seeds of animal-dispersed fruits are adapted to survive digestion by frugivores. For example, seeds can become more permeable to water after passage through an animal's gut; this leads to higher germination rates. Some mistletoe seeds germinate inside the disperser's intestine. In order for frugivores to be good seed dispersers, they must digest fruits without consuming a high proportion of the seeds. Many seed-dispersing animals have specialized digestive systems to process fruits, which leave seeds intact; some bird species have shorter intestines to pass seeds from fruits, while some frugivorous bat species have longer intestines. Some seed-dispersing frugivores have short gut-retention times, others can alter intestinal enzyme composition when eating different types of fruits.
Plants invest energy into the production of fruits. Plants have evolved to encourage mutualist frugivores to consume their fruit for seed dispersal, but evolved mechanisms to decrease consumption of fruits when unripe and from non-seed-dispersing predators. Predators and parasites of fruit include seed predators and microbial frugivores. Plants have physical adaptations. Physical deterrents: Cryptic coloration Unpalatable textures Resins and saps Repellent substances, hard outer coats, thornsChemical deterrents: Chemical deterrents in plants are called secondary metabolites. Secondary metabolites are compounds produced by the plant that are not essential for the primary processes, such as growth and reproduction. Toxins might have evolved to prevent consumption by animals that disperse seeds into unsuitable habitats, to prevent too many fruits from being eaten per feeding bout by preventing too many seeds being deposited in one site, or to prevent digestion of the seeds in the gut of the animal.
Secondary chemical defenses are divided into three categories: nitrogen-based, carbon-based terpenes, carbon-based phenolics. Examples of secondary chemical defenses in fruit: Capsaicin is a carbon-based phenolic compound only found in plant genus Capsicum. Capsaicin is responsible for the pungent, hot "flavor" of peppers and inhibits growth of microbes and invertebrates. Cyanogenic glycosides are nitrogen-based compounds and are found in 130 plant families, but not in the fruit of all the plants, it is found in the red berries of the genus Ilex. It can inhibit electron transport, cellular respiration, induce vomiting and mild narcosis in animals. Emodin is a carbon-based phenolic compound in plants like rhubarb. Emodin can be cathartic or act as a laxative in humans, kills dipteran larvae, inhibits growth of bacteria and fungi, deters consumption by birds and mice. Starch is a polysaccharide, converted to fructose as the fruit ripens. Birds are a main focus of frugivory research. An article by B.
A. Loisell and J. G. Blake, Potential Consequences of Extinction of Frugivorous Birds, discusses the im
ETH Zurich is a science, technology and mathematics university in the city of Zürich, Switzerland. Like its sister institution EPFL, it is an integral part of the Swiss Federal Institutes of Technology Domain, directly subordinate to Switzerland's Federal Department of Economic Affairs and Research; the school was founded by the Swiss Federal Government in 1854 with the stated mission to educate engineers and scientists, serve as a national center of excellence in science and technology and provide a hub for interaction between the scientific community and industry. In the 2019 edition of the QS World University Rankings ETH Zurich is ranked 7th in the world, is ranked 10th in the world by the Times Higher Education World Rankings 2018. In the 2019 QS World University Rankings by subject it is ranked 3rd in the world for engineering and technology, 1st for Earth & Marine Science; as of August 2018, 32 Nobel laureates, 4 Fields Medalists, 1 Turing Award winner have been affiliated with the Institute, including Albert Einstein.
It is a founding member of the IDEA League and the International Alliance of Research Universities and a member of the CESAER network. ETH was founded on 7 February 1854 by the Swiss Confederation and began giving its first lectures on 16 October 1855 as a polytechnic institute at various sites throughout the city of Zurich, it was composed of six faculties: architecture, civil engineering, mechanical engineering, forestry, an integrated department for the fields of mathematics, natural sciences and social and political sciences. It is locally still known as Polytechnikum, or as Poly, derived from the original name eidgenössische polytechnische Schule, which translates to "federal polytechnic school". ETH is a federal institute; the decision for a new federal university was disputed at the time. In the beginning, both universities were co-located in the buildings of the University of Zürich. From 1905 to 1908, under the presidency of Jérôme Franel, the course program of ETH was restructured to that of a real university and ETH was granted the right to award doctorates.
In 1909 the first doctorates were awarded. In 1911, it was given Eidgenössische Technische Hochschule. In 1924, another reorganization structured the university in 12 departments. However, it now has 16 departments. ETH Zurich, the EPFL, four associated research institutes form the "ETH Domain" with the aim of collaborating on scientific projects. ETH Zurich is ranked among the top universities in the world. Popular rankings place the institution as the best university in continental Europe and ETH Zurich is ranked among the top 1-5 universities in Europe, among the top 3-10 best universities of the world. ETH Zurich has achieved its reputation in the fields of chemistry and physics. There are 32 Nobel Laureates who are associated with ETH; the most recent Nobel Laureate is Richard F. Heck, awarded the Nobel Prize in chemistry in 2010. Albert Einstein is its most famous alumnus. In 2018, the QS World University Rankings placed ETH Zurich at 7th overall in the world. In 2015, ETH was ranked 5th in the world in Engineering and Technology, just behind the Massachusetts Institute of Technology, Stanford University, Cambridge University and National University of Singapore.
In 2015, ETH ranked 6th in the world in Natural Sciences, in 2016 ranked 1st in the world for Earth & Marine Sciences for the second consecutive year. In 2016, Times Higher Education World University Rankings ranked ETH Zurich 9th overall in the world and 8th in the world in the field of Engineering & Technology, just behind the Massachusetts Institute of Technology, Stanford University, California Institute of Technology, Princeton University, Cambridge University, Imperial College London and Oxford University. In a comparison of Swiss universities by swissUP Ranking and in rankings published by CHE comparing the universities of German-speaking countries, ETH Zurich traditionally is ranked first in natural sciences, computer science and engineering sciences. In the survey CHE ExcellenceRanking on the quality of Western European graduate school programmes in the fields biology, chemistry and mathematics, ETH was assessed as one of the three institutions to have excellent graduate programmes in all considered fields, the other two being the Imperial College London and the University of Cambridge.
ETH Zurich had a total budget of 1.885 billion CHF in the year 2017. For Swiss students, ETH is not selective in its undergraduate admission procedures. Like every public university in Switzerland, ETH is obliged to grant admission to every Swiss resident who took the Matura. Applicants from foreign countries are required to take either the reduced entrance exam or the comprehensive entrance exam although some applicants from several European countries are exempted from this rule. An applicant can be admitted to ETH without any verifiable educational records by passing the comprehensive entrance exam; as at all universities in Switzerland, the academic year is divided into two semesters. Examinations are held durin
Maximum likelihood estimation
In statistics, maximum likelihood estimation is a method of estimating the parameters of a statistical model so the observed data is most probable. This is done by finding the value of the parameter θ that maximizes the likelihood function L, the joint probability of the observed data y, over a parameter space Θ; the point θ ^ ∈ Θ. The logic of maximum likelihood is both intuitive and flexible, as such the method has become a dominant means of inference within much of the quantitative research of the social and medical sciences; as an example, suppose that we are interested in the heights of adult female penguins, but are unable to measure the height of every penguin in a population. Assuming that the heights are distributed with some unknown mean and variance, the mean and variance can be estimated with MLE while only knowing the heights of some sample of the overall population. MLE would accomplish that by taking the mean and variance as parameters and finding particular parametric values that make the observed results the most probable given the normal model.
If the likelihood function is differentiable with respect to θ, the derivative test for determining maxima can be applied. In some cases, the first-order conditions of the likelihood function can be solved explicitly. Under most circumstances, numerical methods will be necessary to find the maximum of the likelihood function. From the point of view of Bayesian inference, MLE is a special case of maximum a posteriori estimation that assumes a uniform prior distribution of the parameters. In frequentist inference, MLE is one of several methods to get estimates of parameters without using prior distributions. Priors are avoided by not making probability statements about the parameters, but only about their estimates, whose properties are defined by the observations and the statistical model; the method of maximum likelihood is based on the likelihood function, L. We are given a statistical model, i.e. a family of distributions, where θ denotes the parameter for the model. The method of maximum likelihood finds the values of the model parameter, θ, that maximize the likelihood function, L. Intuitively, this selects the parameter values that make the data most probable.
The method defines a maximum likelihood estimate: θ ^ ∈. In practice, it is convenient to work with the natural logarithm of the likelihood function, called the log-likelihood: ℓ = ln L, or the average log-likelihood: ℓ ^ = 1 n ln L; the hat over ℓ indicates. Indeed, ℓ ^ estimates the expected log-likelihood of a single observation in the model. An MLE is the same regardless of whether we maximize the likelihood or the log-likelihood, because log is increasing. For many models, a maximum likelihood estimator can be found as an explicit function of the observed data x. For many other models, however, no closed-form solution to the maximization problem is known or available, an MLE can only be found via numerical global optimization. For some problems, there may be multiple values. For other problems, no maximum likelihood estimate exists: either the log-likelihood function increases without reaching a supremum value, or the supremum does exist but is outside the bounds of Θ, the set of acceptable parameter values.
A maximum likelihood estimator is an extremum estimator obtained by maximizing, as a function of θ, the objective function ℓ ^