... or does there need to be data on the left side of the mode? The logic to "not unimodal" would be that there must be a peak to be unimodal and there's no peak if the data only decreases on one side.
1 Answer
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Yes; it is. See: https://en.wikipedia.org/wiki/Unimodality Unimodality requires a unique highest value, even if it is attained at an edge. For example, the exponential distribution is considered unimodal.