Fig 1. Symptom scales comparison and correlation.

The difference between the two groups for a given variable was analyzed by a two-sided t-test. The standardized difference in group means is the difference between the mean of the Post-Treatment Lyme disease (PTLD) symptoms group minus the mean of the recovered group, divided by its standard error. This standardization is done so that variables measured on different scales can be compared, and the strength of evidence for a difference between groups can be quantified. Values above 0 on the y-axis indicate higher mean scores for the PTLD symptoms group, while values below 0 indicate higher mean scores for the recovered group. P-values are given to indicate the statistical magnitude of the effect.