eli5: What is multimodal distribution? With examples, please 🙂
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Mode refers to the peak (most numerous) value or range. Multimodal is just saying that there is more than one peak to the data as plotted.
The height of human adults is a good example, because there will be two peaks in the data distribution, one corresponding to the modal (most common) height for women and the other corresponding to the modal height from men.
There are lots of reasons why a distribution could display more than one peak. In the human height example, the existence of a bimodal distribution is a strong indicator of some external factor influencing the measurements (there are actually two different populations being measured and combined together, and the two populations are distinct with regard to the measured parameters, the things being measured). The existence of the bimodal distribution is declaring that something is responsible that has not been considered (distinctions by population was not expected for some reason or other, so time to figure out what that might be).
In rare cases, the multimodal (many peaks) distribution can be due to sampling bias (different sampling methods can lead to collection of items that are different simply because the sampling methods each favor one size range over another, and they are different ranges, so the results cover different ranges).
If you were to extrapolate this idea to its full extent (measuring of many populations which are not actually related yet quite different respecting the thing being measured), you would get a distribution that is basically noise, what is called noise, literally. Background results that have nothing to do with what you want to know and show no clear patterns. Numerous factors are about equal in importance and yet produce completely different things to each other, so you get a more or less random set of results that cover a wide range in values with no obvious pattern.
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