Wearables measure optical and motion signals, but most familiar outputs—including sleep stages, calories and sometimes HRV—are algorithmic estimates. Here is how to interpret them.
Smart scales can measure weight accurately while producing much less certain body-fat estimates. Here is how impedance, hydration, equations and measurement conditions affect the result.
Wearable HRV can be useful for tracking personal trends, but the result depends on how pulse intervals are sensed, filtered, summarized, and collected.
Calibration connects a sensor’s readings to known reference values under specified conditions. Validation asks whether the complete device performs adequately for its intended users, setting, metric, and health-related purpose.
