Inference by Eye: Confidence Intervals and How to Read Pictures of Data.

TLDR

Confidence intervals are underused in psychology, despite their potential to improve research communication. The study aims to clarify how to interpret error bars in figures and to propose seven rules for inferential use. The authors outline general principles and specific guidelines for interpreting overlap of confidence intervals on independent group means. Adopting interval estimation could substantially improve research communication in psychology.

Abstract

Wider use in psychology of confidence intervals (CIs), especially as error bars in figures, is a desirable development. However, psychologists seldom use CIs and may not understand them well. The authors discuss the interpretation of figures with error bars and analyze the relationship between CIs and statistical significance testing. They propose 7 rules of eye to guide the inferential use of figures with error bars. These include general principles: Seek bars that relate directly to effects of interest, be sensitive to experimental design, and interpret the intervals. They also include guidelines for inferential interpretation of the overlap of CIs on independent group means. Wider use of interval estimation in psychology has the potential to improve research communication substantially.