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	Effect Size
		Effect size (ES) is a name given to a family of indices that measure the magnitude of a treatment effect.
		Effect sizes can also be thought of as the average percentile standing of the average treated (or experimental) participant relative to the average untreated (or control) participant.
		Measures of effect size in ANOVA are measures of the degree of association between and effect (e.g., a main effect, an interaction, a linear contrast) and the dependent variable.
	web.uccs.edu /lbecker/Psy590/es.htm (3340 words)

	ED230A Effect Size
		Effect size can also be thought of as the average percentile standing of the average treatment (or experimental) participant relative to the average untreated (or control) participant.
		An effect size of 1.7 indicates that the mean of the treatment group is at the 95.5 percentile of the untreated group.
		Effect sizes can also be interpreted in terms of the percent of nonoverlap of the treatment group's scores with those of the untreated group.
	www.gseis.ucla.edu /courses/ed230a2/notes/effect.html (545 words)

	Effect Size and Clinical/Practical Significance
		Effect size is a name given to a group of statistics that measure the magnitude of a treatment effect.
		Effect sizes can also be interpreted as the percent of nonoverlap of the treated group's distribution with that of the control group.
		An effect size of 0.8 indicates a nonoverlap of 47.4% in the distributions, whereas an effect size of 1.7 indicates a nonoverlap of 75.4% in the distributions.
	www.umdnj.edu /idsweb/shared/effect_size.htm (433 words)

	New View of Statistics: On The Fly for Means
		Recall that the effect size is the difference between the means divided by the average standard deviation of the two groups.
		You've got a value for the effect size, and you've done it with the minimum number of subjects, and it's practically unbiased by doing it on the fly, and you know that its confidence interval is narrow enough that it can't overlap more than two steps (colors) on the qualitative magnitude scale.
		With the small sample sizes that are possible, the error in the standard deviation is proportionally larger, so the confidence interval of the effect size ends up large after all, so we lose the benefit of the high reliability and end up with larger sample sizes again.
	www.sportsci.org /resource/stats/ssmean.html (2371 words)

	Design and Analysis of Ecological Experiments
		Effect size measures in the d – family are appropriate when effect sizes arise from the assessment of the effect of a discrete covariate such as in an ANOVA or t-test.
		Effect size measures in the r – family are appropriate when effect sizes arise from the assessment of the effect of a continuous covariate such as in regression or correlation.
		Effect size is calculated for each experiment as the difference between the means of two groups of individuals, divided by their pooled standard deviation to standardize the effect among studies.
	userwww.sfsu.edu /~efc/classes/biol710/meta/meta-analysis.htm (3891 words)

	Effect Size and Meta-Analysis. ERIC Digest.
		An effect size expresses the increase or decrease in achievement of the experimental group (the group of students who are exposed to a specific instructional technique) in standard deviation units.
		A study that shows an effect size of 1.0 thus means a percentile gain of 34 points one standard deviation above the mean encompasses 34 percent of the scores provided one can assume the average for the group is the 50th percentile.
		Another way of interpreting effect size is to consider an effect size of.20 as small, an effect size of.50 as medium, and an effect size of.80 as large (Cohen, 1988).
	www.ericdigests.org /2003-4/meta-analysis.html (1537 words)

	effect size power analysis sample size
		The nature of the effect size will vary from one statistical procedure to the next (it could be the difference in cure rates, or a standardized mean difference, or a correlation coefficient) but its function in power analysis is the same in all procedures.
		Indeed, while the effect observed in prior studies might help to provide an estimate of the true effect it is not likely to be the true effect in the population - if we knew that the effect size in these studies was accurate, there would be no need to run the new study.
		Since the effect size used in power analysis is not the "true" population value, the researcher may elect to present a range of power estimates.
	www.power-analysis.com /effect_size.htm (779 words)

	Effect Size Calculation Help for Dissertation Students & Researchers
		An effect size is the size of the relationship between two variables and is usually defined as the difference in mean outcomes between the treatment and control group.
		Effect size is also an indicator of the strength of the difference between two groups.
		Given the importance of measuring effect size, it is important that it is conducted properly and explained in simple language.
	www.researchconsultation.com /effect-size-calculation-help.asp (313 words)

	APA effect size
		Third, and perhaps most importantly, interpreting the effect sizes in a given study facilitates the evaluation of how a study's results fits into existing literature, the explicit assessment of how similar or dissimilar results are across related studies, and potentially informs judgment regarding what study features contributed to similarities or differences in effects.
		Although there is a class of effect sizes that Kirk (1996) labelled "miscellaneous" (e.g., the odds ratios that are so important in loglinear analyses), there are two major classes of effect sizes for parametric analyses.
		It should also be noted that Cohen (1988) provided rules of thumb for characterizing what effect sizes are small, medium, or large, as regards his impressions of the typicality of effects in the social sciences generally.
	www.coe.tamu.edu /~bthompson/apaeffec.htm (1360 words)

	Effect size and rehabilitation research Journal of Rehabilitation - Find Articles
		For example, the 5th edition of the American Psychological Association Manual (APA, 2001) emphasizes the necessity to include some index of effect size or strength of relationship in psychological research further stating that the failure to report indicators of effect or strength of relationship to be a "defect" (p.5).
		As editors of the Journal we also feel that these indicators of effect size have direct application to rehabilitation research and therefore will require that indicators of effect be incorporated into empirically-based research articles that are submitted for publication to the Journal.
		The utilization of effect size indicators for research published in the journal will allow the readers and rehabilitation researchers to better utilize the research published in the journal to make programmatic decisions or further research in the area of rehabilitation.
	findarticles.com /p/articles/mi_m0825/is_4_70/ai_n8681400 (842 words)

	An Educator's Guide to Evaluating Claims about Educational Software
		Effect sizes also give us a sense of whether a gain in achievement is important (i.e., is it big or small).
		As a quick rule of thumb, an effect size of 0.30 or greater is considered to be important in studies of educational programs.
		A small effect size may be of important practical significance if the intervention is relatively inexpensive compared to competing options, if the effect occurs among all groups of students, and if the effect accumulates over time.
	www.ncrel.org /tech/claims/measure.html (476 words)

	Effect Size of Symptom Status in Withdrawal of Typical Antipsychotics and Subsequent Clozapine Treatment in Patients ...
		Effect Size of Symptom Status in Withdrawal of Typical Antipsychotics and Subsequent Clozapine Treatment in Patients With Treatment-Resistant Schizophrenia -- Pickar and Bartko 160 (6): 1133 -- Am J Psychiatry
		Effect Size of Symptom Status in Withdrawal of Typical Antipsychotics and Subsequent Clozapine Treatment in Patients With Treatment-Resistant Schizophrenia
		and a mean change of 8% and an effect size of 0.18 in the latter.
	ajp.psychiatryonline.org /cgi/content/full/160/6/1133 (3451 words)

	Why use Effect Sizes instead of Significance Testing in Program Evaluation?
		Effect sizes are standardised and can be compared to benchmarks such as effect sizes from other types of interventions.
		Typically an effect size of.8 is considered to be large,.5 as moderate and.2 as small (Cohen, 1977).
		Effect sizes of.2,.5 and.8 indicate that the mean of the treated group is at the 58th, 69th and 79th percentiles of the untreated group respectively.
	www.wilderdom.com /research/effectsizes.html (1047 words)

	Language Log: Gabby guys: the effect size
		One way to measure the size of such group differences is to scale the difference between the group averages according to the amount of variation within each group's distribution.
		For the mixed-sex FECP1 conversations, the effect size of the diference between the number of words used by men and the number of words used by women (expressed in terms of Cohen's d) is 0.203.
		Effect sizes, measured in standard deviations of separation between low and middle SES group performance, on the composite measures of the seven different neurocognitive systems assessed in this study.
	itre.cis.upenn.edu /~myl/languagelog/archives/003607.html (1563 words)

	Effect size
		By standardising the effect, the effect size becomes dimensionless (and that can be helpful when pooling data).
		The effect size can be just the difference between the mean values of the two groups, divided by the standard deviation, as below, but there are other ways to calculate effect size in other circumstances.
		Generally, the larger the effect size, the greater is the impact of an intervention.
	www.jr2.ox.ac.uk /bandolier/booth/glossary/effect.html (232 words)

	effect sample size - p-value - power analysis
		For example, a p-value of.02 means that, assuming that the treatment has no effect, and given the sample size, an effect as large as the observed effect would be seen in only 2% of studies.
		Assuming the null is false (and the true effect is given by the effect size used in computing power) we would expect a type II error to occur in the proportion of studies denoted by one minus power, and this error rate is known as beta.
		Figure 2 shows power as a function of sample size for three levels of alpha (assuming an effect size of 30% vs. 50%, which is the intermediate effect size in the prior figure).
	www.poweranalysis.com /p_value.htm (570 words)

	The Edmonton Public Schools Small Class Size Study - Overview (Site not responding. Last check: )
		The supplemental data at the back of the Small Class Size Project Final Report shows that of the 161 students who participated, 88 students increased their performance, while 59 students achieved the same levels and the performance of 14 students was lower.
		Much of the literature cited suggests that the effects of reducing class size are ambiguous and many studies indicate that little, if any, measurable improvement in student achievement results.
		Parents attributed a variety of benefits to reduced class size and would naturally prefer their children to be taught in smaller classes.
	www.education.gov.ab.ca /ClassSize (864 words)

	Effect Size
		An effect size is an indication of the amount of variability in the dependent variable that can be accounted for by the independent variable.
		You may have noticed that we are using the correlation coefficient as an effect size.
		You find that the effect size associated with the main effect of applicant appearance is.50 and the effect size associated with the main effect of qualifications is.25.
	chiron.valdosta.edu /mawhatley/3600/es.htm (304 words)

	effect size
		The larger the difference expected between the two population means, the greater the effect size; the smaller the variance within the two populations, the greater the effect size.
		Definition 2: The extent to which the two populations do not overlap is called the effect size because it is the extent to which the experiment has an effect of separating the two populations.
		Effect size convention (Cohen, 1988): Cohen came up with some effect size conventions based on the effects found in psychology research in general.
	www.chsbs.cmich.edu /k_han/psy511/d.htm (226 words)

	effect
		There are two major classes of effect sizes (not counting a third "miscellaneous" category described by Kirk (1996)): (a) variance-accounted-for effect sizes analogous to a squared correlation coefficient, and (b) standardized mean differences.
		The important consideration is to report and interpret effect sizes as part of analyses, and to make clear to the reader specifically which effect size is being reported.
		What makes a given effect size noteworthy depends both on (a) the context of the particular study (e.g., life-or-death medication effects vs. smiling and touching behaviors of adolescents in fast food restaurants) and (b) the value system of a given researcher.
	www.coe.tamu.edu /~bthompson/effect.html (1147 words)

	Compute the treatment effect (or effect size) automatically
		The program will compute the effect size from each of them and (to the extent possible) allow you to include them all in the same analysis.
		While most meta-analyses work with effect sizes (which assess the relationship between two variables) some are used to estimate a risk, rate, or mean in one group (for example, “What is the risk of Lyme disease?”).
		In addition to being able to work with recognized effects (such as odds ratios and mean differences) the program is able to work with generic point estimates which may be analyzed either in their original scale or on a log scale.
	www.meta-analysis.com /pages/features/compute_effect.html (1074 words)

	MMU - Research Design, Biol Sci:Power analyses (Site not responding. Last check: )
		Power analysis is important for sample size determination because it is used to estimate the probability that an experiment will be able to reject a false null hypothesis, i.e.
		Effect size is the difference between the null and alternative hypotheses, essentially this is related to the magnitude of effect that is considered to be of biological significance.
		In the simplest case, a comparision of two means, the effect size is measured as a dimensionless index termed d.
	obelia.jde.aca.mmu.ac.uk /new_rd/contents/power1.htm (1208 words)

	Overview of the SpryEffects.js library
		The order in which the assembled effects begin is determined by the order in which they were added to the Cluster effect.
		Although the effects of the Cluster are triggered in chained order, the execution of the effects can execute in parallel if they were added as parallel effects.
		A Spry effect accepts two parameters: a reference to the HTML element on which the effect is performed, and additional options.
	labs.adobe.com /technologies/spry/articles/effects_coding/index.html (1721 words)

	Effect Size
		The classical calculation for effect size is the difference between the means of the treatment and control group divided by the standard deviation of either of the groups or the pooled standard deviation, assuming that the two groups are homogenous.
		An effect size of 1 means that the treatment group outscored the control group by a full standard deviation.
		One of the statisticians who devised the effect size referred to an effect size of.2 as small,.5 as medium, and.8 as large.
	www.waterford.org /corporate_pages/Research_effectSize.jsp (172 words)

	Effect size measures provide a standardized index of how much impact treatments actually have on the dependent variable (Site not responding. Last check: )
		Effect size measures provide a standardized index of how much impact treatments actually have on the dependent variable.
		By expressing the difference in group means in standard deviation units, the d statistic provides a simple metric that allows you to compare treatment effects from different studies, areas or research, etc., without having to keep track of the units of measurement used in different studies or areas of research.
		The effects of class size on achievement or of juvenile delinquency programs on delinquency outcomes are similarly small.
	www.personal.psu.edu /faculty/k/r/krm10/effectsize1 (367 words)

	Stats: Quick sample size calculations
		This ratio is called the effect size or the standardized effect size.Your sample size per group is 16 divided by the square of the effect size.
		The effect size is 0.2, and the required sample size per group is 400 (=16/0.04).
		The sample size that provides 80% for detecting a two week shift in breast feeding duration is actually 394, not 400.
	www.childrensmercy.org /stats/size/quick.asp (1664 words)

	Correlation: Effect size (Site not responding. Last check: )
		Effect size or "strength of effect" refers to the magnitude or strength of the treatment (the independent variable).
		You can get a good idea of the strength of an effect by looking at the descriptive statistics (that is why it is very important to include them when describing research results).
		It might not be a strong effect, or not matter very much.
	psychology.ucdavis.edu /SommerB/sommerdemo/correlation/effectsize.htm (294 words)

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