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Topic: Degrees of freedom (statistics)


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In the News (Tue 29 Dec 09)

  
 Degrees of freedom
The concept of degrees of freedom is central to the principle of estimating statistics of populations from samples of them.
"Degrees of freedom" is commonly abbreviated to df.
When this principle of restriction is applied to regression and analysis of variance, the general result is that you lose one degree of freedom for each parameter estimated prior to estimating the (residual) standard deviation.
www.statsdirect.com /help/basics/degrees_of_freedom.htm   (319 words)

  
 Encyclopedia topic: Degrees of freedom   (Site not responding. Last check: 2007-10-11)
The three usages are linked historically and through the underlying mathematics (A science (or group of related sciences) dealing with the logic of quantity and shape and arrangement) through the concept of dimensionality (The spatial property of having dimensions), but they are not identical.
In statistics (A branch of applied mathematics concerned with the collection and interpretation of quantitative data and the use of probability theory to estimate population parameters), degrees of freedom are the number of values in probability distribution (additional info and facts about probability distribution) s that are free to be varied.
Examples of this statistical parameter (additional info and facts about statistical parameter) include the chi-square distribution (additional info and facts about chi-square distribution), the F-distribution (additional info and facts about F-distribution), Student's t-distribution (additional info and facts about Student's t-distribution), and the beta distribution (additional info and facts about beta distribution) that underlies them.
www.absoluteastronomy.com /encyclopedia/d/de/degrees_of_freedom.htm   (541 words)

  
 Degrees of Freedom--SAS   (Site not responding. Last check: 2007-10-11)
Galfo (1985) viewed degrees of freedom as the representation of the quality in the given statistic, which is computed using the sample X values.
Rawlings (1988) associated degrees of freedom with each sum of squares (in multiple regression) as the number of dimensions in which that vector is "free to move." Y is free to fall anywhere in n-dimensional space and, hence, has n degrees of freedom.
For example, one degree of freedom is lost when we estimate the population mean using the sample mean; two degrees of freedom are lost when we estimate the standard error of estimate (in regression) using Y-hat (one degree of freedom for the Y-intercept and one degree of freedom for the slope of the regression line).
seamonkey.ed.asu.edu /~alex/computer/sas/df.html   (2591 words)

  
 HKLNA Project - Useful Statistics
This statistic is utilized to test for the statistical significance of clustered patterns for a large number of clustering routines.
The sum of two statistically independent random variables with chi-square distributions is another randomvariable with a chi-squre distribution whose number of degrees of freedom is equal to the sum of the degrees of freedom of both variables.
The degrees of freedom of the Student - t are the same as those of the random variable with chi-square distribution.
homepage.mac.com /moogoonghwa/earth/current/hklna/ff/statistics/statistics.html   (291 words)

  
 [No title]
Degrees of freedom are a function of such factors as the number of subjects and the number of groups.
The degrees of freedom for the F ratio are a function of the number of groups and the number of subjects.
The formula for degrees of freedom for a two dimensional chi square is (R - 1) (C - 1), where R equals the number of rows in the contingency table and C equals the number of columns in the contingency table.
www.bsu.edu /classes/malone/id705/fourteen.htm   (3911 words)

  
 875: Degrees of freedom (DOFs) in COMSOL Multiphysics
It is often desirable to be able to estimate the number of degrees of freedom based on the number of elements in the model.
This means that the number of degrees of freedom is given by the number of nodes multiplied by the number of dependent variables.
Note that the number of degrees of freedom is not the only factor determining the memory requirements and the solution time of a problem.
www.comsol.com /support/knowledgebase/875.php   (441 words)

  
 Degrees of Freedom
Thus the degrees of freedom to determine the mean for 100 samples is n-1 or 99.
For example, the degrees of freedom to estimate variability from one observation would be zero, i.e., it is impossible to estimate variability.
Degrees of freedom of n - 1 is required when taking a sample from a population because when taking the limited size sample, you have only a very slight chance of picking the extreme data values of the population.
www.isixsigma.com /forum/showthread.asp?messageID=33443   (2309 words)

  
 Degrees Of Freedom
The phrase "degrees of freedom" is used in three different branches of science: in physics and physical...
Degrees of Freedom (df) Statisticians use the terms "degrees of freedom" to describe the number of values in the final calculation of a...
The term "degrees of freedom", the theme of this essay, is a technical term that refers to a...
www.eligiblembas.com /mba_resources/degrees-of-freedom.html   (608 words)

  
 chi square degrees of freedom   (Site not responding. Last check: 2007-10-11)
...the degrees of freedom of the table from which our chi square value is derived.
To determine the chi-square value indicating a probability Q of non-chance occurrence for an experiment with d degrees of freedom, enter Q...
F distribution is denoted by the degrees of freedom for the numerator Chi-square and the degrees of freedom for the denominator Chi-square.
www.cvtruth.com /chi-square-degrees-of.html   (385 words)

  
 SPCTool
The relationship between degrees of freedom and the coefficient of variation is the key to answering the question of how much data you need.
The terminology "degrees of freedom" cannot be explained without using higher mathematics, so the reader is advised to simply use it as a label that quantifies the amount of data utilized by a given computation.
Since degrees of freedom are directly related to the number of data used, Figure 2 suggests that when we have fewer than 10 d.f., we will want to revise and update our limits as additional data become available.
www.qualitydigest.com /june97/html/spctool.html   (1191 words)

  
 SJSU Biometrics: Publications
We use this extreme case to demonstrate that the "degrees of freedom" is insufficient to characterize performance.
Increasing the "degrees of freedom" for both densities does not increase the accuracy of the device.
We might seek to correct the assertion that "degrees of freedom" is a measure of device performance by incorporating the difference in the parameter p between the genuine and impostor binomial distributions.
www.engr.sjsu.edu /biometrics/publications_degrees.html   (1361 words)

  
 Degrees of freedom - TheBestLinks.com - Analysis of variance, Integer, Mathematics, Mechanical engineering, ...   (Site not responding. Last check: 2007-10-11)
Degrees of freedom - TheBestLinks.com - Analysis of variance, Integer, Mathematics, Mechanical engineering,...
Degrees of freedom, Analysis of variance, Integer, Mathematics, Mechanical...
The phrase "degrees of freedom" is used in three different branches of science: in physics and physical chemistry, in mechanical and aeronautical engineering, and in statistics.
www.thebestlinks.com /Degrees_of_freedom.html   (445 words)

  
 c29b2 adumb.doc
Statistics on the sampling of the degrees of freedom are recorded during the md simulations and periodically used to update the umbrella potential such that uniform sampling of the degrees of freedom can be expected.
The statistics read must be from adaptive umbrella sampling simulations with the same parameters as the present one, in particular, the same degrees of freedom have to be used as umbrella coordinates.
A few statistics that differ significantly from the rest of the statistics can be due to problems with the convergence caused by the extrapolation or due to the occurrence of rare events.
www.uwm.edu /People/dxie/Charmm/c29b2/adumb.html   (2681 words)

  
 : Class Statistics
Computes absolute size of half of a student-t confidence interval for given degrees of freedom, probability, and observed value.
Returns chi-squared probability for given value and degrees of freedom.
(The probability that the chi-squared variate will be greater than x for the given degrees of freedom.) Adapted from unixstat by Gary Perlman.
www.dcs.napier.ac.uk /~peter/vldb/doc/weka/core/Statistics.html   (254 words)

  
 Com 3310 | ANOVA
The primary thing that was being calculated was called a "statistic." Once you calculated a statistic, you had to go to a table to look up the significance value associated with it.
F is a statistic, a value that we used to calculate by hand so we could look up the significance level in a table.
These conventions persist although the ideas of statistics as indidual values to be calculated on the way to determining a signicance level is obsolete.
comm2.fsu.edu /faculty/comm/mcclung/anova.htm   (929 words)

  
 Degree of Freedom
The number of degrees of freedom in a problem, distribution, etc., is the number of parameters which may be independently varied.
If it is an average, how come we divide by the degrees of freedom (n-1) This causes you to lose a degree of freedom and you should divide by n-1
It is important to appreciate the concept of "degrees of freedom".
www.indexpark.com /degree/degree-of-freedom   (318 words)

  
 The UNIVARIATE Procedure : Statistical Computations
The W statistic is the ratio of the best estimator of the variance (based on the square of a linear combination of the order statistics) to the usual corrected sum of squares estimator of the variance (Shapiro, 1965).
The Anderson-Darling statistic and the Cramer-von Mises statistic belong to the quadratic class of EDF statistics.
degrees of freedom (Tukey and McLaughlin 1963, Dixon and Tukey 1968).
www.okstate.edu /sas/v7/sashtml/books/pguide/zte-comp.htm   (2471 words)

  
 Ed 602 - Lesson 10 - One Sample Statistical Tests
In this lesson we are going to move on and look at inferential statistics to test hypotheses concerned with comparing a single sample (instead of a single score) with some population parameter.
The t statistic is not distributed normally like the z statistic is but is distributed as (guess what) the t-distribution, also referred to as student's distribution.
Degrees of freedom is a mathematical concept that involves the amount of freedom you have to substitute various values in an equation.
www.mnstate.edu /wasson/ed602lesson10.htm   (1009 words)

  
 Degrees of Freedom Explanation [TimeWeb]
Degrees of freedom are calculated from the size of the sample.
Every time a statistic is calculated from a sample, one degree of freedom is used up.
It is the case that in a t distribution with 20 degrees of freedom, 95 % of all t values will lie between 2.09 and -2.09.
www.bized.ac.uk /timeweb/digging/dig_source_dof.htm   (297 words)

  
 Reporting Statistics in APA Style   (Site not responding. Last check: 2007-10-11)
Chi-Square statistics are reported with degrees of freedom and sample size in parentheses, the Pearson chi-square value (rounded to two decimal places), and the significance level:
First report the between-groups degrees of freedom, then report the within-groups degrees of freedom (separated by a comma).
(Degrees of freedom for the t-test is N-k-1 where k equals the number of predictor variables.) It is also customary to report the percentage of variance explained along with the corresponding F test.
www.ilstu.edu /~jhkahn/apastats.html   (462 words)

  
 Multimedia Projects: Degree of freedom   (Site not responding. Last check: 2007-10-11)
degrees of freedom in terms of sample size and dimensionality
Every quantitative-based research paper requires reporting of degrees of freedom associated with the test results such as "F(df1, df2)," yet very few people understood why it is essential to do so.
Failure to understand "degrees of freedom" has a side effect: Students and inexperienced researchers mis-interpreted a "perfect-fitted" model or an "over-fitted" model as a good model.
seamonkey.ed.asu.edu /~alex/multimedia/df_flash.html   (203 words)

  
 Mplus Discussion >> Degrees of freedom
is data dependent because it draws on the estimates, their derivatives, and the asymptotic covariance matrix of the sample statistics with the aim of choosing the degrees of freedom that gives a trustworthy chi-square-based p value.
The degrees of freedom for the MLMV estimator are not computed in the regular way.
In covariance structure models, degrees of freedom are basd on the number of restrictions imposed on the covariance matrix not on sample size.
www.statmodel.com /discussion/messages/11/21.html?1099678940   (606 words)

  
 Univariate Statistics - One Sample Tests
The thing that determines the shape of the distribution is something called the degrees of freedom.
By definition, degrees of freedom are the number of scores that are free to vary.
But don't get too frazzled, the basic concepts stay the same: 1) the shape of a non-normal sampling distribution is determined by the number of degrees of freedom, and 2) the degrees of freedom are used to more accurately estimate a population parameter in those cases when it is not known.
www.uwsp.edu /psych/cw/statmanual/onesample.html   (879 words)

  
 Basic Statistics Review - Unit 1 - 155.a
Degrees of freedom refer to how may cases in the sample are free to vary.
The sample in this instance looses one degree of freedom for the sample mean.
All but one of the numbers in the sample may vary, but one is constrained to a particular value to obtain a sample mean of 50.
www.msu.edu /user/sw/statrev/strv155a.htm   (250 words)

  
 Two-Way ANOVA
While the statistical formulas necessary for conducting a two-way ANOVA are only slightly more complicated than those required for one-way ANOVA calculations, this author believes that for beginning students they are best left for computer software to solve.
Notice that the Between groups Sum of Squares is 31.2667, with three levels for this variable and two degrees of freedom, producing a Mean Square of 15.63333.
Compare the F statistic for Dosage in the two-way output of 4.51 (which is statistically significant), with the nonsignificant F value of 2.78 from the one-way analysis.
espse.ed.psu.edu /statistics/Chapters/Chapter12/Chap12.html   (2387 words)

  
 Definition Of Degrees Of Freedom   (Site not responding. Last check: 2007-10-11)
The phrase "degrees of freedom" is used in three different branches of science: in physics and physical chemistry, in mechanical and aerospace engineering, …
… in regression, the working definition of degrees of freedom involves the … Cramer (1946) defined degrees of freedom as the rank of a quadratic form.
… and because each joint position is usually defined with a single variable, the number of joints equals the number of degrees of freedom.
www.hamilton2000.hamilton.on.ca /definition-of-degrees-of-freedom.html   (458 words)

  
 Stats: Degrees of Freedom
Degrees of freedom is a measure of how much precision an estimate of variation has.
A general rule is that the degrees of freedom decrease when we have to estimate more parameters.
This causes you to lose a degree of freedom and you should divide by n-1 rather than n.
www.cmh.edu /stats/ask/df.asp   (239 words)

  
 [No title]
These statistics are normally defined in terms of the squared canonical correlations which are the eigenvalues of the matrix H*inv(H+E).
Degrees of freedom are computed assuming all linear combinations contribute to the Lambda and Trace statistics, so the F tests for those statistics are conservative.
A liberal test statistic with conservative degrees of freedom and a conservative test statistic with liberal degrees of freedom yield at best an approximate p value, which is indicated by a "~" before the p value.
www.utdallas.edu /~murthi/sas/conj1.lst   (463 words)

  
 Degrees of Freedom   (Site not responding. Last check: 2007-10-11)
Statistians use the terms "degrees of freedom" to describe the number of values in the final calculation of a statistic that are free to vary.
To calculate the s-square of a random sample, we must first calculate the mean of that sample and then compute the sum of the several squared deviations from that mean.
For these reasons, the statistic s-square is said to have only (n - 1) degrees of freedom.
www.sysurvey.com /tips/statistics/degrees.htm   (149 words)

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