eli5: What is multimodal distribution? With examples, please 🙂
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I don’t think there is a clear unambiguous definition that captures all cases (correct me on that if there is one), but a multimodal distribution is one where there are multiple “humps”, basically. “Bimodal” means there are exactly two.
For example, the distribution of “time it takes for you to trim a nail” – your fingernails grow something like 4x faster than toenails, so there will be a lot of probability mass near one value, and a lot of it near some other value 4x larger, with not a lot inbetween. You can’t really simplify that by replacing it with a single gaussian. Or the distribution of Euler angles of a flipped coin – the “azimuth” will be uniformly distributed, but the other angle will be either 0 or 180 degrees, for heads/tails. Or the distribution of speeds in a multi-lane highway – depending on how traffic flows, there could be one “mode” per lane, or one for cars and one for large trucks, or they all mix together. Or sometimes the distribution of pixel colors in an image – large similarly shaded areas will correspond to peaks in a histogram, and for many images there will be multiple distinct ones. Or the distribution of flow rate of a sink – it’s either on or off most of the time, and the “on” amount varies, but it’s rarely left to trickle.
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