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title: "4.5 Normal distribution of measurements"
canonical: "https://wiki.groenkennisnet.nl/space/TAB/283377755/4.5%20Normal%20distribution%20of%20measurements"
format: markdown
---
Many traits of animals show a normal distribution. This means that the distribution is symmetric and can be characterized by a mean and variance. Below and above this mean you see the same number of animals. And by the fact that further away from the mean you see a decreasing number of animals with this measured unit. Graphically it can be expressed as:                         

![image](media://bdc6083c-b9eb-4dc4-9358-aa035c31b975)

  
In such a normal distribution you see that 68 per cent of the animals has a value for this trait within one standard deviation from the mean; 95 per cent within two standard deviations from the mean and 99.7 per cent within three standard deviations from the mean.