LARGE TRIAL BIAS:
A bias that occurs when one makes decisions about the quality of study based solely on the fact that the size of the sample is large, without evaluating other characteristics1. Such that, if one prefers larger studies, they may overemphasize the importance of the results if the study is large, or if one generally dislikes large studies, they may deemphasize the importance of the results if the study is large1, and/or focus on the weaknesses of the study instead of its strengths.
Large Trial Bias is a specific type of Interpretive Bias, is similar to Small Trial Bias, and is applicable to all study designs, not just clinical trials as the name indicates. Large Trial Bias is a problem, as large studies are not necessarily more or less valid compared to ones that are small; since sample size and study quality/validity are different concepts. Sample size is related to issues of statistical significance only, and not clinical meaningfulness; both are different and important for assessing study quality and validity. Also see: Interpretive Bias, Small Trial Bias, Significance Bias, and Wrong Sample Size Bias.
Reference:
1. Earl-Slater A. The Handbook of Clinical Trials and Other Research. Abingdon: Radcliffe Medical Press Ltd. 2002. (Link to Reference)