Generalized Eta and Omega Squared Statistics: Measures of Effect Size for Some Common Research Designs

Department of Educational Psychology, College of Education, University of Georgia, Athens, GA 30602-7143, USA.
Psychological Methods (Impact Factor: 4.45). 01/2004; 8(4):434-47. DOI: 10.1037/1082-989X.8.4.434
Source: PubMed


The editorial policies of several prominent educational and psychological journals require that researchers report some measure of effect size along with tests for statistical significance. In analysis of variance contexts, this requirement might be met by using eta squared or omega squared statistics. Current procedures for computing these measures of effect often do not consider the effect that design features of the study have on the size of these statistics. Because research-design features can have a large effect on the estimated proportion of explained variance, the use of partial eta or omega squared can be misleading. The present article provides formulas for computing generalized eta and omega squared statistics, which provide estimates of effect size that are comparable across a variety of research designs.

Download full-text


Available from: James Algina
  • Source
    • "There is some controversy surrounding effect size for ANOVAs as there is evidence that eta squared has been misreported in the past in communications research (Levine & Hullett, 2002) which is likely to be the case for landscape preference studies. Alternatives effect sizes have been developed (e.g.Bakeman, 2005;Olejnik & Algina, 2003) however not for the current studies design. As a result, effect size is reported here in partial eta squared (Á p 2 ) as this is consistent with previous landscape preference research and recommended when other methods are not feasible (Lakens, 2013), which allows for comparison with studies that use a similar design. "
    [Show abstract] [Hide abstract]
    ABSTRACT: This research investigated the perceptual interaction of combining sound with 3D landscape visualizations. Images sourced from Google Earth at St. James's Park, London, UK, showing terrain only, terrain with built form or terrain with primarily vegetation were paired with four sound conditions using recordings from the park (i.e. ‘no sound’, anthropogenic, mechanical and natural). Perceived realism and preference were evaluated using a survey delivered via the Internet and in a controlled laboratory environment (N=199 total). Analysis using repeated measures ANOVA indicated the interaction of sound and 3D visualizations significantly alters environmental perception both positively and negatively. Sounds and visuals that are congruent receive higher realism and preference ratings while the more incongruent the combination is, the lower the corresponding ratings. The lowest realism and preference ratings are given to visualizations showing terrain only combined with speech. The highest realism rating
    Full-text · Article · Apr 2016 · Landscape and Urban Planning
    • "Again the position in field was considered as a nested factor and had four levels (labelled as 3, 2,1 and 0, where 0 is the location over the well and 3 is the location furthest from the well). The significance of individual factors and interactions between factors were considered and the magnitude of the effects calculated using generalised ω 2 (Olejnik and Algina, 2003). The underlying assumption of ANOVA is that all variance is random and that factors and interactions have to be proved (at given probability ) to be significant. "
    [Show abstract] [Hide abstract]
    ABSTRACT: This study considered the fugitive emissions of methane (CH4) from former oil and gas exploration and production wells drilled to exploit conventional hydrocarbon reservoirs onshore in the UK. This study selected from the 66% of all onshore wells in the UK which appeared to be properly decommissioned (abandoned) that came from 4 different basins and were between 8 and 79 years old. The soil gas above each well was analysed and assessed relative to a nearby control site of similar land use and soil type. The results showed that of the 102 wells considered 30% had soil gas CH4 at the soil surface that was significantly greater than their respective control. Conversely, 39% of well sites had significant lower surface soil gas CH4 concentrations than their respective control. We interpret elevated soil gas CH4 concentrations to be the result of well integrity failure, but do not know the source of the gas nor the route to the surface. Where elevated CH4 was detected it appears to have occurred within a decade of it being drilled. The flux of CH4 from wells was 364 ± 677 kg CO2eq/well/year with a 27% chance that the well would have a negative flux to the atmosphere independent of well age. This flux is low relative to the activity commonly used on decommissioned well sites (e.g. sheep grazing), however, fluxes from wells that have not been appropriately decommissioned would be expected to be higher.
    No preview · Article · Jan 2016 · Science of The Total Environment
  • Source
    • "Interpretation of strength of evidence provided by BFs (anecdotal, substantial, strong, very strong, or decisive evidence) comes fromWetzels et al. (2011). To measure effect sizes, generalized eta-squared (Olejnik and Algina, 2003) is used. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Handled objects automatically activate afforded responses. The current experiment examined whether objects that afford a response are also prioritized for attentional processing in visual search. Targets were pictures of coffee cups with handles oriented either to the right or the left. Subjects searched for a target, a right-handled vs. left-handled coffee cup, among a varying number of distractor cups oriented in the opposite direction. Responses were faster when the direction of target handle and the key press were spatially matched than mismatched (stimulus-response compatibility (SRC) effect), but object affordance did not moderate slopes of the search functions, indicating the absence of attentional prioritization effect. These findings imply that handled objects prime afforded responses without influencing attentional prioritization.
    Full-text · Article · Jan 2016 · Frontiers in Integrative Neuroscience
Show more

We use cookies to give you the best possible experience on ResearchGate. Read our cookies policy to learn more.