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  "body": "\n## Summary\n\nDirectional statistics is the part of statistics whose observations are directions, angles or rotations.\nSuch data live on the circle, on a [[sphere|T62369RFH6]] or on other manifolds, not on a line, so the usual mean and variance can mislead.\nMeans are taken of unit vectors instead of angles, and models such as the [[von Mises–Fisher distribution|V8ZZ7A2FMF]] replace the normal distribution.\nApplications include wind directions, animal navigation, times of day and orientations of rocks.\n\n## Explanations\n\n### L1 human\n\nTwo wind directions of $350$ and $10$ degrees both point almost due north.\nTheir ordinary average is $180$ degrees, due south, which is plainly wrong.\nDirectional statistics treats each direction as an arrow of length $1$ and adds the arrows.\nThe sum of these two arrows points due north, the sensible answer.\n",
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