FACTOID # 28: Austin, Texas has more people than Alaska.
 
 Home   Encyclopedia   Statistics   States A-Z   Flags   Maps   FAQ   About 
   
 
WHAT'S NEW
RELATED ARTICLES
People who viewed "Statistical" also viewed:
 

SEARCH ALL

FACTS & STATISTICS    Advanced view

Search encyclopedia, statistics and forums:

 

 

(* = Graphable)

 

 


Encyclopedia > Statistical
For Wikipedia statistics, see m:Statistics

Statistics is the science and practice of developing human knowledge through the use of empirical data expressed in quantitative form. It is based on statistical theory which is a branch of applied mathematics. Within statistical theory, randomness and uncertainty are modelled by probability theory. Because one aim of statistics is to produce the "best" information from available data, some authors consider statistics a branch of decision theory. Statistical practice includes the planning, summarizing, and interpreting of observations, allowing for variability and uncertainty.

Contents

Origin

The word statistics comes from the modern Latin phrase statisticum collegium (lecture about state affairs), from which came the Italian word statista, which means "statesman" or "politician" (compare to status) and the German Statistik, originally designating the analysis of data about the state. It acquired the meaning of the collection and classification of data generally in the early nineteenth century. The collection of data about states and localities continues, largely through national and international statistical services; in particular, censuses provide regular information about the population.


Statistical methods

We describe our knowledge (and ignorance) mathematically and attempt to learn more from whatever we can observe. This requires us to

  1. plan our observations to control their variability (experiment design),
  2. summarize a collection of observations to feature their commonality by suppressing details (descriptive statistics), and
  3. reach consensus about what the observations tell us about the world we observe (statistical inference).

In some forms of descriptive statistics, notably data mining, the second and third of these steps become so prominent that the first step (planning) appears to become less important. In these disciplines, data often are collected outside the control of the person doing the analysis, and the result of the analysis may be more an operational model than a consensus report about the world.


Probability

The probability of an event is often defined as a number between one and zero. In reality however there is virtually nothing that has a probability of 1 or 0. You could say that the sun will certainly rise in the morning, but what if an extremely unlikely event destroys the sun? What if there is a nuclear war and the sky is covered in ash and smoke?


We often round the probability of such things up or down because they are so likely or unlikely to occur, that it's easier to recognize them as a probability of one or zero.


However, this can often lead to misunderstandings and dangerous behaviour, because people are unable to distinguish between, e.g., a probability of 10−4 and a probability of 10−9, despite the very practical difference between them. If you expect to cross the road about 105 or 106 times in your life, then reducing your risk of being run over per road crossing to 10−9 will make you safe for your whole life, while a risk per road crossing of 10−4 will make it very likely that you will have an accident, despite the intuitive feeling that 0.01% is a very small risk.


Use of prior probabilities of 0 (or 1) causes problems in Bayesian statistics, since the posterior distribution is then forced to be 0 (or 1) as well. In other words, the data is not taken into account at all! As Lindley puts it, if a coherent Bayesian attaches a prior probability of zero to the hypothesis that the Moon is made of green cheese, then even whole armies of astronauts coming back bearing green cheese cannot convince him. Lindley advocates never using prior probabilities of 0 or 1. He calls it Cromwell's rule, from a letter Oliver Cromwell wrote to the synod of the Church of Scotland on August 5th, 1650 in which he said "I beseech you, in the bowels of Christ, consider it possible that you are mistaken."


Specialized disciplines

Some sciences use applied statistics so extensively that they have specialized terminology. These disciplines include:

Statistics form a key basis tool in business and manufacturing as well. It is used to understand measurement systems variability, control processes (as in statistical process control or SPC), for summarizing data, and to make data-driven decisions. In these roles it is a key tool, and perhaps the only reliable tool.


Software

Modern statistics is supported by computers to perform some of the very large and complex calculations required.


Whole branches of statistics have been made possible by computing, for example neural networks.


The computer revolution has implications for the future of statistics, with a new emphasis on 'experimental' statistics.


A list of statistical packages in common use

See also

References

Lindley, D. Making Decisions. John Wiley. Second Edition 1985. ISBN 0471908088


External links

General sites and organizations

  • Statlib: Data, Software and News from the Statistics Community (Carnegie Mellon) (http://lib.stat.cmu.edu/)
  • International Statistical Institute (http://www.cbs.nl/isi/)
  • The Probability Web (http://www.mathcs.carleton.edu/probweb/probweb.html)

Link collections

Online courses and textbooks

Wikibooks has a textbook about:
Wikibooks School of Mathematics has more about this subject:
Statistics

Statistical software

Other resources


  Results from FactBites:
 
WIN - Statistics (2822 words)
To understand these statistics, it is necessary to know how overweight and obesity are defined and measured, something this publication addresses.
For age-adjusted rates, statistical procedures are used to remove the effect of age differences when comparing two or more populations at one point in time, or one population at two or more points in time.
Most of the statistics presented here represent the economic cost of overweight and obesity in the United States in 1995, updated to 2001 dollars.[10] Unless otherwise noted, these statistics are adapted from Wolf and Colditz,[11] who based their data on existing epidemiological studies that defined overweight and obesity as a BMI > 29.
Statistics - MSN Encarta (1432 words)
Simple forms of statistics have been used since the beginning of civilization, when pictorial representations or other symbols were used to record numbers of people, animals, and inanimate objects on skins, slabs, or sticks of wood and the walls of caves.
Registration of deaths and births was begun in England in the early 16th century, and in 1662 the first noteworthy statistical study of population, Observations on the London Bills of Mortality, was written.
At present, statistics is a reliable means of describing accurately the values of economic, political, social, psychological, biological, and physical data and serves as a tool to correlate and analyze such data.
  More results at FactBites »

 
 

COMMENTARY     


Share your thoughts, questions and commentary here
Your name
Your comments

Want to know more?
Search encyclopedia, statistics and forums:

 


Press Releases |  Feeds | Contact
The Wikipedia article included on this page is licensed under the GFDL.
Images may be subject to relevant owners' copyright.
All other elements are (c) copyright NationMaster.com 2003-5. All Rights Reserved.
Usage implies agreement with terms, 1022, m