There are two kinds of comparison to show how inaccurate is the automated blood pressure monitor. One is to compare with the traditional sphygmomanoter that is the gold standard for indirect BP measurement. The difference is what people can feel when they compare their own machine reading and doctor's reading. Another is to compare the reading from two automated BPMs. If these two machines give two different readings, there is at least one inaccruate machine. So, here is the infographics based on two independent researches. You can get the conclusion by yourself.