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Topic: Statistical significance


In the News (Wed 21 Aug 19)

  
  Statistical Significance Terms
Statistical methods are used to estimate the probability that chance alone accounts for the differences in outcomes.
Clinical vs. Statistical Significance: Statistical significance means the likelihood that the difference found between groups could have occurred by chance alone.
In most clinical trials, a result is statistically significant if the difference between groups could have occurred by chance alone in less than 1 time in 20.
www.musc.edu /dc/icrebm/statisticalsignificance.html   (1108 words)

  
 Statistical Significance
The first part simplifies the concept of statistical significance as much as possible; so that non-technical readers can use the concept to help make decisions based on their data.
In contrast the high significance level for type of vehicle (.001 or 99.9%) indicates there is almost certainly a true difference in purchases of Brand X by owners of different vehicles in the population from which the sample was drawn.
While this logic passes the common sense test, the mathematics behind statistical significance do not actually guarantee that 1-p gives the exact probability that there is a difference is the population.
www.surveysystem.com /signif.htm   (1299 words)

  
 Statistical Significance vs. Practical Significance of Research Results
The importance of significant p values is further diminished by the fact that they are easily influenced by sample size, the value of p used as the criterion for rejecting the null hypothesis, and whether the test of statistical significance is one-tailed or two-tailed.
The term "practical significance" implies a research result that will be viewed as having importance for the practice of education or, in other words, it will be viewed as important by teachers, school administrators, policy makers, and others concerned about the day-to-day workings of education and efforts to improve it.
Because statistically significant results are valued by journal editors and the research community in general, individual researchers might feel a subtle coercion to design their study to maximize the likelihood of achieving these results (by increasing the sample size and other methods mentioned earlier in the paper).
www.uoregon.edu /~mgall/statistical_significance_v.htm   (3825 words)

  
  What is Statistical Significance?   (Site not responding. Last check: 2007-10-02)
Statistical significance is a mathematical tool used to determine whether the outcome of an experiment is the result of a relationship between specific factors or due to chance.
Statistical significance is commonly used in the medical field to test drugs and vaccines and to determine causal factors of disease.
Statistics are the mathematical calculations of numeric sets or populations that are manipulated to produce a probability of the occurrence of an event.
www.wisegeek.com /what-is-statistical-significance.htm   (517 words)

  
 II. Sampling Error and Statistical Significance   (Site not responding. Last check: 2007-10-02)
As indicated in the footnotes, significant differences are noted by "a" (significant at the.05 level of significance) and "b" (significant at the.01 level of significance).
Also, keep in mind that while a level of significance equal to.05 is used to determine statistical significance in these tables, large differences associated with slightly higher p-values (specifically those between.05 and.10) may be worth noting along with the p-values.
Furthermore, statistically significant differences are not always meaningful, because the magnitude of difference may be small or because the significance may have occurred simply by chance.
www.oas.samhsa.gov /nhsda/ar18t056.htm   (614 words)

  
 Statistical Significance vs. Practical Significance of Research Results
The importance of significant p values is further diminished by the fact that they are easily influenced by sample size, the value of p used as the criterion for rejecting the null hypothesis, and whether the test of statistical significance is one-tailed or two-tailed.
My argument thus far is this: (1) tests of statistical significance tell us virtually nothing about the importance of a research result; and (2) ES tells us about magnitude of difference, which is important, but it is difficult for practice-oriented practitioners to comprehend and too limited in the information it conveys to them.
Because statistically significant results are valued by journal editors and the research community in general, individual researchers might feel a subtle coercion to design their study to maximize the likelihood of achieving these results (by increasing the sample size and other methods mentioned earlier in the paper).
darkwing.uoregon.edu /~mgall/statistical_significance_v.htm   (3825 words)

  
 Statistical Significance
When a statistic is significant, it simply means that you are very sure that the statistic is reliable.
Significance is a statistical term that tells how sure you are that a difference or relationship exists.
In these situations, the word "significant" is used to advise a client to take note of a particular difference or relationship because it may be relevant to the company's strategic plan.
www.statpac.com /surveys/statistical-significance.htm   (894 words)

  
 CancerGuide: The Significance of Statistical Significance
Statistical significance is about deciding whether differences observed between groups in experiments are "real" or whether they might well just be due to chance.
Different statistical tests are used depending on what kind of data is being tested (for instance something with a discrete outcome like responded versus didn't respond requires a different test than something with a continuous outcome like survival time) and what statistic is being tested - say the mean or the median.
You observe that the patients who choose treatment A have a statistically significant advantage in survival compared to those who chose treatment B. But suppose treatment A and B are really no different in their effect on survival, but A has more difficult side effects.
www.cancerguide.org /significance.html   (4121 words)

  
 The Barrow Quarterly Article 11-2-5
Statistical analysis provide additional information to be incorporated into the logical framework of the theory and may prompt the investigator to revise or elaborate research plans.
Furthermore, there is a degree of subjectivity in statistical analysis given that the investigator must define parameters such as the significance or alpha (a) level; the power level (1-b) based on a sample size, which may reflect choice or convenience; the effect size based upon the clinical area, and the experimental design.
Both clinical and statistical significance depend upon the initial research hypothesis in terms of the decisions to be made in planning, analysis, and interpretation.
www.emergemd.com /bniq2/article.asp?article_ref_id=11-2-5   (4262 words)

  
 The Concept of Statistical Significance Testing. ERIC/AE Digest.
For example, the influence of sample size on statistical significance may be acknowledged by a researcher, but this insight is not conveyed when interpreting results in a study with several thousand subjects.
Statistical significance testing requires subjective judgment in setting a predetermined acceptable probability (ranging between 0 and 1.0) of making an inferential error caused by the sampling error--getting samples with varying amounts of "flukiness"--inherent in sampling.
Since the actual population parameters are not known, we must assume what the parameters are, and in statistical significance testing we assume the parameters to be correctly specified by the null hypothesis, i.e., we assume the null hypothesis to be exactly true for these calculations.
www.ericdigests.org /1995-1/testing.htm   (1521 words)

  
 Common Sense about Statistical Significance
In the discussion that follows, the reader will be shown that obtaining a statistically significant result does not necessarily imply that the research is practically significant and that results that are practically significant can be obtained from research that is not statistically significant.
This small difference may not be statistically significant however, in pro golf, a difference of one stroke in a tournament could result in significantly larger earnings (which would result in a practically significant result for the golfer).
The change is statistically significant and the result is also practically significant but the individual (or researcher) has to make a decision about which processor to purchase based on personal preferences and financial considerations.
www.wtc.edu /online/bcanada/assign4a04.htm   (2725 words)

  
 Tests of Statistical Significance
Statistical significance means that there is a good chance that we are right in finding that a relationship exists between two variables.
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.
www.csulb.edu /~msaintg/ppa696/696stsig.htm   (4571 words)

  
 Statistical and Clinical Significance   (Site not responding. Last check: 2007-10-02)
Statistical significance relates to the question of whether or not the results of a statistical test meets an accepted criterion level.
I believe we come to a natural, but erroneous, interpretation of statistical significance as a measure of the effect magnitude we intuitively know that somehow it is the magnitude of the effect that is fundamentally important.
Clinically significant improvement could be defined as movement from one area (severe) to another (moderate) without having to move all the way to the normal range.
web.uccs.edu /lbecker/Psy590/clinsig.htm   (2697 words)

  
 Demographic Research - Reporting Statistical Significance
Significance asterisks are a poor substitute for this.
This journal accepts the fact that much higher p-values indicate statistical significance in very small data sets, while for the enormous sets typical of register data for populations with millions of members, much smaller p-values than 0.05 may be needed to indicate important features in the data.
We also would like to see the interpretation of a study based not on statistical significance, or lack of it, for one or more study variables, but rather on careful quantitative consideration of the data in light of competing explanations for the findings.
www.demographic-research.org /info/reporting_statistical_significance.htm   (1066 words)

  
 More on the Importance of Statistical Significance
Although the reported association is statistically significant, there were 29 other reported associations that either were not positive (i.e., the relative risks were 1.0 or less) or were not statistically significant.
These 19 positive associations, regardless of statistical significance, could then be used to support a causal link between EMF exposure and cancer.
If this were a game, changing the rules by eliminating statistical significance changes the score from 29-1 against causation, to 19- 11 for causation.
www.junkscience.com /news/emf-data-dredging.html   (342 words)

  
 ECP - Primer on Statistical Significance and P Values
Statistical significance (meaning a low P value) depends on three factors: the main effect itself and the two factors that make up the variance.
Although it is tempting to equate statistical significance with clinical importance, critical readers should avoid this temptation.
And because significance is powerfully influenced by the number of observations, statistically significant changes can be observed with trivial changes in important outcomes.
www.acponline.org /journals/ecp/julaug01/primer.htm   (764 words)

  
 Statistical Significance   (Site not responding. Last check: 2007-10-02)
When experiments are properly designed, it is typical to specify a statistical test on the results and only consider the test to be a success if there is less than 5% (or sometimes 1%) chance that the result could have occurred by chance.
It is important to note that just because the result is not statistically significant we cannot assume that the radishes didn't have a beneficial effect.
Statistical procedures take into account the number of ways an experiment can succeed, but they aren't valid if the experimenter only decides what she is measuring after she knows what would work.
www.truthpizza.org /science/experim/signif.htm   (553 words)

  
 PA 765: Significance
Significance is the percent chance that a relationship found in the data is just due to an unlucky sample, such that if we took another sample we might find nothing.
Significance testing is not appropriate for enumerations or non-random samples because it only deals with the the chance of Type I error based on a random sample.
Thus significance has a different meaning when, for example, the confidence interval is the entire range of the data, as compared to the situation where the confidence interval is only ten percent of the range.
www2.chass.ncsu.edu /garson/pa765/signif.htm   (1232 words)

  
 Methodology: Statistical significance   (Site not responding. Last check: 2007-10-02)
Statistical significance was determined by conducting chi-square and one-way analysis of variance tests.
For a relationship to be considered statistically significant, it must meet a minimum level of significance, which in this case was set at.05.
In other words, if a relationship is statistically significant at the.05 level, there would be less than a 5-percent probability that the relationship occurred by chance.
www.ojjdp.ncjrs.org /pubs/96natyouthgangsrvy/meth_6.html   (97 words)

  
 Statistical Rationale   (Site not responding. Last check: 2007-10-02)
Descriptive statistics are used to summarize the results using means, standard deviations, frequencies and other methods which describe the central tendency and variability of the data.
Significance tests state the probability that the results are due to chance.
Statistical tests such as t-test, F-ratio, and chi-square ultimately lead to a p-value which is used to make a statement about the statistical signinficance of the results.
research.med.umkc.edu /tlwbiostats/rationale.html   (159 words)

  
 Statistical Significance   (Site not responding. Last check: 2007-10-02)
Significance tests are performed to see if the null hypothesis can be rejected.
If the null hypothesis is rejected, then the effect found in a sample is said to be statistically significant.
A statistically significant effect is not necessarily practically significant.
davidmlane.com /hyperstat/A71266.html   (77 words)

  
 Statistical Significance Calculator   (Site not responding. Last check: 2007-10-02)
The level of statistical significance is the same as the probability that the event would occur by chance in a nondiscriminatory setting.
Following the lead of social scientists, the courts typically require a demonstration of statistical significance at the 0.05 or 5 percent level, to permit an inference of discrimination.
In general, the significance is the probabilty that there would be as large a disparity, if employment decisions were independent of membership in the protected class.
www.bardwellconsulting.com /page.php3?index=tools&index2=chi   (682 words)

  
 Power in statistics and statistical significance
Statistical comparison tests can be used to characterize the data we observe (in the Love Canal health study, the data are the number of deaths, cancers, and different birth outcomes).
When the phrase "statistical significance" is used, it means the difference is not likely to be due to chance.
The ability to statistically detect a difference when the difference truly exists (that is, not due to chance) is called the power of the test.
www.health.state.ny.us /environmental/investigations/love_canal/power.htm   (1253 words)

  
 Statistical significance
The level of statistical significance is determined by the probability that this has not, in fact, happened.
Therefore a large value of P represents a small level of statistical significance and vice versa.
In experiments where we are obliged to resort to statistics it is therefore proper procedure to define a level of significance at which a correlation will be deemed to have been proven, though the choice is often actually made after the event.
www.numberwatch.co.uk /significance.htm   (471 words)

  
 Significance Tests Simplified
If an observed significance level (P value) is less than 0.05, reject the hypothesis under test; if it is greater than 0.05, fail to reject the null hypothesis.
Groups whose difference is not statistically significant are reported as being "the same" or we are told that "there is no difference between the groups"!
Statistical significance is irrelevant if the effect is of no practical importance.
www.tufts.edu /~gdallal/sigtest0.htm   (529 words)

  
 Elementary Concepts in Statistics
The statistical significance of a result is the probability that the observed relationship (e.g., between variables) or a difference (e.g., between means) in a sample occurred by pure chance ("luck of the draw"), and that in the population from which the sample was drawn, no such relationship or differences exist.
Using less technical terms, one could say that the statistical significance of a result tells us something about the degree to which the result is "true" (in the sense of being "representative of the population").
Statistical significance represents the probability that a similar outcome would be obtained if we tested the entire population.
www.statsoft.com /textbook/esc.html   (4450 words)

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