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Topic: Statistical tests


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  Statistical Tests   (Site not responding. Last check: 2007-10-21)
Statistical tests, rather than cluster analysis, are the right tool for this purpose.
Permutation testing is an approach that is widely applicable and copes with distributions that are far from Normal; this approach is particularly useful for microarray studies because it can be easily adapted to estimate significance levels for many genes in parallel.
The p-value for the gene is the fraction of cases in which the randomly permuted samples give a test statistic for that gene, at least as extreme as the one that occurs in the properly labelled samples.
discover.nci.nih.gov /microarrayAnalysis/Statistical.Tests.jsp   (5323 words)

  
 7.1.3. What are statistical tests?
A test statistic is computed from the data and tested against pre-determined upper and lower critical values.
If the test statistic is greater than the upper critical value or less than the lower critical value, the null hypothesis is rejected because there is evidence that the mean linewidth is not 500 micrometers.
This chapter gives methods for constructing test statistics and their corresponding critical values for both one-sided and two-sided tests for the specific situations outlined under the scope.
www.itl.nist.gov /div898/handbook/prc/section1/prc13.htm   (645 words)

  
 rng7
The purpose of this test is to determine whether the length of the longest run of ones within the tested sequence is consistent with the length of the longest run of ones that would be expected in a random sequence.
The purpose of this test is to determine whether the number of occurrences of the 2m m-bit overlapping patterns is approximately the same as would be expected for a random sequence.
The purpose of the test is to determine whether the cumulative sum of the partial sequences occurring in the tested sequence is too large or too small relative to the expected behavior of that cumulative sum for random sequences.
csrc.nist.gov /rng/rng9.html   (1133 words)

  
 Tests of Statistical Significance
A second method of reporting the results of tests for statistical significance is to report the test and its value, the degrees of freedom, and the p-value at the bottom of the contingency table or printout showing the data on which the calculations were based.
Tests for statistical significance are used to estimate the probability that a relationship observed in the data occurred only by chance; the probability that the variables are really unrelated in the population.
Tests for statistical significance are used because they constitute a common yardstick that can be understood by a great many people, and they communicate essential information about a research project that can be compared to the findings of other projects.
www.csulb.edu /~msaintg/ppa696/696stsig.htm   (4571 words)

  
 Selecting Statistical Tests
This test is the non-parametric parallel to the repeated measures AOV.
This test is the non-parametric parallel to the AOV.
This is a mathematical procedure not a statistical test.
www.sahs.utmb.edu /pellinore/intro_to_research/wad/sel_test.htm   (2635 words)

  
 Statistical Tests in SPSS
Each section gives a brief description of the aim of the statistical test, when it is used, an example showing the SPSS commands and SPSS (often abbreviated) output with a brief interpretation of the output.
The Wilcoxon-Mann-Whitney test is the non-parametric version of the independent samples t-test and can be used when you do not assume that the dependent variable is a normally distributed interval variable (you only assume that the variable is ordinal).
Likewise, the test of the overall model is not statistically significant, LR chi-squared - 0.56, p = 0.453.
www.ats.ucla.edu /stat/spss/whatstat/whatstat.htm   (4734 words)

  
 Approximate Statistical Tests for Comparing Supervised Classification Learning Algorithms - Dietterich (ResearchIndex)
These tests are compared experimentally to determine their probability of incorrectly detecting a difference when no difference exists (type I error).
Two widely-used statistical tests are shown to have high probability of Type I error in certain situations and should never be used.
These tests are (a) a test for the difference of two...
citeseer.ist.psu.edu /dietterich98approximate.html   (552 words)

  
 Statistical Hypothesis Testing
Statistical tests always involve Type I (producer's or alpha) and Type II (consumer's or beta) risks.
In statistical testing, the significance level, Type I risk, or alpha risk is the "reasonable doubt." It is the chance of wrongly rejecting the null hypothesis when it is true.
It is the integral of the distribution from 0 to 12.59, and 95 percent of the area under the curve is to the left of 12.59.
www.ganesha.org /spc/hyptest.html   (1256 words)

  
 Knodt's Statistical Help   (Site not responding. Last check: 2007-10-21)
Statistical tests designed for use with ordered data generally do not make stringent assumptions about the nature of the underlying distributions and hence are more conservative than those designed for score data.
The test does not assume that the difference scores are from normal populations with is one of the assumptions of the t-Test.
The test does assume that the population is symmetrical so that the mean is an accurate representation of central tendency, and is equal to the median.
members.aol.com /statware/pubpage.htm   (14045 words)

  
 Statistical Tests   (Site not responding. Last check: 2007-10-21)
It should be noted that the positive result of any particular statistical test does not ``prove'' the randomness of the RNG.
An empirical test can statistically analyze any given random sequence, whereas a theoretical test only considers the properties of a specific RNG algorithm.
test and Kolmogorov-Smirnov test are used to assess uniformity.
www.cs.dartmouth.edu /~akapadia/project2/node12.html   (166 words)

  
 Statistical Tests in SAS
Each section gives a brief description of the aim of the statistical test, when it is used, an example showing the SAS commands and SAS output (often excerpted to save space) with a brief interpretation of the output.
The Wilcoxon-Mann-Whitney test is the non-parametric version of the independent samples t-test and can be used when you do not assume that the dependent variable is a normally distributed interval variable (you need only assume that the variable is ordinal).
This command produces four different test statistics that are used to evaluate the statistical significance of the relationship between the independent variable and the outcome variables.
www.ats.ucla.edu /stat/sas/whatstat/whatstat.htm   (6159 words)

  
 A class of statistical tests for uniform PRNs
The result of the former are vectors of random numbers which will be tested, the result of the later are random vectors from which we deduce the distribution of the test statistic.
As we are thinking of an empirical test that should be evaluated by a computer in a finite amount of time, we have to limit the number of PRNs that are to be tested.
A test with such a critical region would exclude random numbers whose empirical distribution function is either too close to or too far from the theoretical one.
random.mat.sbg.ac.at /~ste/dipl/node25.html   (2074 words)

  
 The Abuse of Statistics in Cryptography
Abuse of statistical tests is most obvious in the design of random number generators (both RNGs and PRNGs) but also can occur when statistical tests are relied on too heavily to judge the quality of intermediate stages and output in hash functions and ciphers.
The first most elementary fact of computational statistics, which any but a snake oil cryptographer should understand, is that there is no such thing as a feasible all purpose statistical test.
This requirement renders such tests far less useful than many seem to think: once we have made this deduction, we gain nothing from a Maurer test except to catch most (but hardly all, and possibly not the most important) innocent mistakes in the deduction or implementation.
szabo.best.vwh.net /statistics.html   (1163 words)

  
 Statistical Tests
The same formula holds for the continuity-corrected test, with the exception that when the noncontinuity-corrected Z and the continuity-corrected Z have opposite signs, the two-tailed p-value is 1.
Since its variance is not weighted by the pooled probabilities, as is the CA test, the FT test can be more useful than the CA test for tests involving only a subset of the groups.
Note, however, that the FISHER exact test is a special case of the exact permutation tests performed by PROC MULTTEST and that these permutation tests allow a stratification variable.
www.asu.edu /sas/sasdoc/sashtml/stat/chap43/sect13.htm   (1664 words)

  
 Journal of Vision - Accurate statistical tests for smooth classification images, by Chauvin, Worsley, Schyns, Arguin, ...
Despite an obvious demand for a variety of statistical tests adapted to classification images, few have been proposed.
We argue that two statistical tests based on random field theory (RFT) satisfy this need for smooth classification images.
We illustrate these tests on classification images representative of the literature from F. Gosselin and P. Schyns (2001) and from A. Sekuler, C. Gaspar, J. Gold, and P. Bennett (2004).
journalofvision.org /5/9/1   (185 words)

  
 Choosing Statistical Tests   (Site not responding. Last check: 2007-10-21)
This page provides an outline of the factors relevant to the choice of statistical tests and a set of three charts which may be used to guide your selection of a test.
In situations where one variable is studied, the chart below may guide your selection of a statistical test.
In situations where two variables are studied, the chart below may guide your selection of a statistical test.
research.med.umkc.edu /tlwbiostats/choosetest.html   (140 words)

  
 Statistics and Statistical Graphics Resources
Statistical Society of Canada Maintains a page of links to statistics pages, conferences, statistical organizations, government agencies, Canadian university statistics departments, and Case Studies to be explored at annual meetings.
Discusses a new approach to the introductory statistics course based on the concepts of entities, properties of entities, and relationships between properties of entities.
Bureau of Justice Statistics home page The Bureau of Justice Statistics web site is a comprehensive collection of statistics about US crime, victims, criminals, courts, police, jails and prisons.
www.math.yorku.ca /SCS/StatResource.html   (7463 words)

  
 Picking the Right Statistical Test   (Site not responding. Last check: 2007-10-21)
Simple instructions on how to pick the right statistical test for your data, for journalists and other writers who might not know math.
If you want to understand why a specific test is the right choice, try Intuitive Biostatistics: Choosing a statistical test, an online chapter to a stats textbook.
When you're ready to conduct your test, you'll find links to several nifty web pages that perform stats calculations at www.statpages.net.
www.robertniles.com /stats/tests.shtml   (399 words)

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