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These measurement errors might have a systematic and/or random character. Systematic errors might be caused by differences between animals for example: diet composition, age at measurement, training etc. Random errors, e.g. measurements errors, may cause a low repeatability for a trait. For instance, when when you want to measure the length of an animal, and you repeat this ten times you will see a rather large variation in outcomes. Slight movements of the animal are the cause. When you measure pelvic height, you see a rather small variation in outcomes. Two measures of accuracy of measurement are relevant: repeatability and reproducibility, both are correlations between measures on the same animal.
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