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ERIC Number: EJ896129
Record Type: Journal
Publication Date: 2010
Pages: 25
Abstractor: As Provided
Reference Count: 62
ISSN: ISSN-0211-2159
The Hard but Necessary Task of Gathering Order-One Effect Size Indices in Meta-Analysis
Ortego, Carmen; Botella, Juan
Psicologica: International Journal of Methodology and Experimental Psychology, v31 n2 p291-315 2010
Meta-analysis of studies with two groups and two measurement occasions must employ order-one effect size indices to represent study outcomes. Especially with non-random assignment, non-equivalent control group designs, a statistical analysis restricted to post-treatment scores can lead to severely biased conclusions. The 109 primary studies included in 4 meta-analyses were recovered, and their authors were contacted to request the raw data to calculate the order-one effect size indices. From this total we only got 13 primary studies. The results with the raw data analysis were compared with those performed with the order-zero and order-one indices. Despite the difficulties for gathering the data, the few data sets analyzed show that if the meta-analysis is performed with order-zero indices, the results can be severely misleading. (Contains 4 tables, 1 figure, and 1 footnote.)
University of Valencia. Dept. Metodologia, Facultad de Psicologia, Avda. Blasco Ibanez 21, 46010 Valencia, Spain. Tel: +34-96-386-4100; Web site:
Publication Type: Journal Articles; Reports - Research
Education Level: N/A
Audience: N/A
Language: English
Sponsor: N/A
Authoring Institution: N/A