Figure 1.
Three different confidence intervals (CIs) for two sample means. The raw data are plotted in the center of the figure; dots represent individual data points (five observations per mean; see also Table 2). Panels A and B show CIs that are appropriate for between-subjects designs; Panel C shows a CI that is appropriate for within-subjects designs (pairs of values are indicated by dashed lines in the raw data). Panel A. CIs for individual means (CIM) rely on the standard error (SE) of the corresponding mean. The CIM indicates whether this mean is significantly different from any given (fixed) value. They do not inform about the statistical significance of the difference between the means. Panel B. CI for the difference between the means (CID). The means are significantly different (as judged by t-tests for independent samples) if one mean is not included in the CID around the other mean. Panel C. Within-subjects CI, constructed from the paired difference scores (CIPD). Two means from paired samples are significantly different (as judged by a paired-samples t-test) if one mean is not included in the CIPD around the other mean.