Analysis of Covariance

2021 ◽  
pp. 161-176
Author(s):  
Andy Hector

ANCOVA of designed experiments combines one categorical and one continuous explanatory variable. Panel plots are usually the best way to graphically display ANCOVA designs, with a separate linear regression within each level of the factor. ANCOVA can test for effects of both variables and interactions between them. The chapter focuses on ANCOVA of designed experiments. A detailed analysis is given of a subset of the variables from an experimental study of the effects of low-level atmospheric pollutants and drought on agricultural yields.

1997 ◽  
Vol 12 (2) ◽  
pp. 117-121 ◽  
Author(s):  
I. Ruiz Calatrava ◽  
J. M. Santisteban Valenzuela ◽  
R. J. Gómez-Villamandos ◽  
J. I. Redondo ◽  
J. C. Gómez-Villamandos ◽  
...  

F1000Research ◽  
2013 ◽  
Vol 2 ◽  
pp. 247
Author(s):  
Adam Pedley ◽  
Alex R Wade

Background: A remarkable series of recent papers have shown that colour can influence performance in cognitive tasks. In particular, they suggest that viewing a participant number printed in red ink or other red ancillary stimulus elements improves performance in tasks requiring local processing and impedes performance in tasks requiring global processing whilst the reverse is true for the colour blue. The tasks in these experiments require high level cognitive processing such as analogy solving or remote association tests and the chromatic effect on local vs. global processing is presumed to involve widespread activation of the autonomic nervous system. If this is the case, we might expect to see similar effects on all local vs. global task comparisons. To test this hypothesis, we asked whether chromatic cues also influence performance in tasks involving low level visual feature integration.Methods: Subjects performed either local (contrast detection) or global (form detection) tasks on achromatic dynamic Glass pattern stimuli. Coloured instructions, target frames and fixation points were used to attempt to bias performance to different task types. Based on previous literature, we hypothesised that red cues would improve performance in the (local) contrast detection task but would impede performance in the (global) form detection task. Results: A two-way, repeated measures, analysis of covariance (2×2 ANCOVA) with gender as a covariate, revealed no influence of colour on either task, F(1,29) = 0.289, p = 0.595, partial η2 = 0.002. Additional analysis revealed no significant differences in only the first attempts of the tasks or in the improvement in performance between trials.Discussion: We conclude that motivational processes elicited by colour perception do not influence neuronal signal processing in the early visual system, in stark contrast to their putative effects on processing in higher areas.


2011 ◽  
Vol 27 (1) ◽  
pp. 103-111 ◽  
Author(s):  
Jon Joensen ◽  
Nils Roar Gjerdet ◽  
Steinar Hummelsund ◽  
Vegard Iversen ◽  
Rodrigo Alvaro B. Lopes-Martins ◽  
...  

2015 ◽  
Vol 30 (3) ◽  
pp. 1061-1068 ◽  
Author(s):  
Valéria Regina Gonzalez Sella ◽  
Fernando Russo Costa do Bomfim ◽  
Paula Carolina Dias Machado ◽  
Maria José Misael da Silva Morsoleto ◽  
Milton Chohfi ◽  
...  

1993 ◽  
Vol 24 (3) ◽  
pp. 400-405 ◽  
Author(s):  
B. Goldwasser ◽  
J. Ramon ◽  
S. Engelberg ◽  
D. Ohad ◽  
H. Sharkey ◽  
...  

2009 ◽  
Vol 24 (2) ◽  
pp. 223-237 ◽  
Author(s):  
James G. Booth ◽  
Walter T. Federer ◽  
Martin T. Wells ◽  
Russell D. Wolfinger

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