In some areas where data are used there is remarkably little focus resting on its reliability or interpretation. The ‘CAPTCHA' tests, e.g., ask you to prove your humanity by identifying images such as boats, bicycles, or traffic lights. If your choice, even if correct, differs from that of the machine system, you will be deemed inhuman. In this example, the machine’s error is obvious, though there is no appeal against it if you want to access the website it is guarding. But in other cases, it may not be possible to identify what conclusions either machine learning systems or human analysts are drawing when they place more weight on data than they can bear.