Distributions

Distributions generally describe the shape by a name. this are both the shape of the generating distribution. There are several common distributions" Normal, Student's t, F, Z, χ2.

Distributions have 4 basic moments that describe the distribution.

  1. Mean - Central Tendency of the distribution.
  2. Variance - Dispersion of the distribution.
  3. Skewness - Asymmetry of the data.
  4. Kurtosis - Divergence of the shape from a standard shape (Normal).

Normal Distributions are the most commonly used distribution in statistics. It is a symmetrical bell shaped distribution

Normal distribution with mean

Figure 1. A normal distribution with mean = 100, and standard deviation 15. The mean is the vertical line.


Normal distribution with 1 standard deviation

Figure 2. A normal distribution with mean = 100, and standard deviation 15. One standard deviation is shown in red.


Normal distribution with 2 standard deviations

Figure 3. A normal distribution with mean = 100, and standard deviation 15. Two standard deviations are shown in red.


Normal distribution with 3 standard deviations

Figure 4. A normal distribution with mean = 100, and standard deviation 15. Three standard deviations are shown in red.


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Natural Resources Biometrics by David R. Larsen is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.

Author: Dr. David R. Larsen
Created: August 22, 2014
Last Updated: August 22, 2014