Systematic error
A consistent, directional error that shifts all measurements in the same direction (higher or lower than the true value), caused by faulty equipment, incorrect calibration, or flawed experimental procedure. Systematic errors cannot be reduced by repeating measurements but can be identified and corrected if their cause is found.
Real World
The Hubble Space Telescope launched in 1990 with a mirror ground 2.2 µm too flat — a systematic manufacturing error that shifted every image equally out of focus until corrective optics were installed in 1993.
Exam Focus
Explain that repeating measurements cannot remove systematic errors — examiners specifically look for this distinction from random errors.
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