Bland-Altman plot calculator
One pair per line: method A, then method B. Bias is the mean of A minus B. Limits are bias ± 1.96 SD.
Questions
What is a Bland-Altman plot?
It compares two measurement methods on the same samples. Each point is the average of the two methods against their difference. The middle line is the mean difference, called the bias.
What are the limits of agreement?
The limits shown here are the bias plus and minus 1.96 standard deviations of the differences. About 95% of differences fall between them if the differences are roughly normal.
Does a small bias mean the methods agree?
Not by itself. Look at the limits of agreement. A bias near zero can still hide differences wide enough to matter clinically.
Educational only. Not medical advice, not a regulatory determination, and not a substitute for qualified RA/QA, legal, clinical, or statistical counsel. Bland-Altman plot does not submit to FDA, Notified Bodies, or IRBs.