5.9 Errors

　

Errors is universal in biological measurement Anthropometry is prone to biological errors for six main reasons: 1. Subject posture (very young children) and movement variation 2. Instrument application pressure 3. Differential tissue thickness 4. Diurnal variation 5. Location of bony landmarks by palpation 6. Accuracy of Equipment (Periodic Calibration) Reliability in females is poorer than in males, mainly due to differential tissue thickness and location of bony landmarks by palpation. Accuracy is the extent to which an observer achieves the "true" value of a measurement: 1. compare results with those of a well trained observer (always check  observer error periodically within an anthropometric study) 2. random error 3. constant error (check protocol/technique) Validity constitutes 1. the degree to which an instrument measures what it is purported to measure and 2. the extent to which it fulfills its purpose (Gogia & Braatz 1986)

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