# What is the name for the distribution shape of a histogram with this kind of curvature?

I have a histogram of points with a dip in the center of the bell, seeming to create two bells, or two clusters. What is the name for this kind of shaped distribution? This curve should be normal but doesn't quite seem to be.

• What's the data? Perhaps there's a confounding variable that could explain the bi-modality? May 13, 2016 at 3:06
• @naught101That does seem to be the case. I am investigating. The data is Ted Cruz pct vote win by county in the US primaries. May 13, 2016 at 3:07
• In that case it's probably worth mapping the data.. May 13, 2016 at 3:12
• If the data are percentages of votes, then I don't see why they "should be normal". Different sociodemographics probably come with very different voting patterns. The overall result could have pretty much any shape. May 13, 2016 at 8:04
• "political data" might have almost any distribution depending on what variable you're measuring if you mean things like proportions of people with some political preference ("do you approve of candidate X?", like the ) perhaps across some set of locations (like your counties), I answered that already -- it's bounded and discrete; more specifically a finite mixture of discrete distributions (with rational mixing proportions). That's about all you can say. It might in some cases make sense to approximate it as a mixture of binomial distributions. That would be the first thing I'd try. ... ctd Jun 26, 2017 at 23:21

It could be a bimodal distribution

Or then it could just be the a run of the mill normal distribution as the dip in the middle doesn't appear to be that big.

Image Bimodal.png by Maksim, from Wikimedia commons; licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license

• How do we translate S.D. values into percentage and something like that results in bimodalty following a mapping of data.
– user10619
May 13, 2016 at 5:01
• @subash "Bimodal" simply means "has two modes" -- there's more than one bimodal distribution, so if I understand what you're saying there (it's somewhat unclear) then your question doesn't have a unique answer. May 13, 2016 at 7:02
• The image from your post appears to be taken from wikimedia commons, authored by user Maksim (it was used in the Wikipedia article "multimodal distribution"). Both the conditions of the license and StackExchange's own standards require proper attribution when you use work like this. Please attribute the authorship or replace the plot. (You're free to use this one I just generated - i.stack.imgur.com/RdFuk.png ) Feb 3, 2017 at 2:28
• @Glen_b - thanks for the heads up. Does the current update confirm with the standards? I'm not sure if I should attribute the article or the file itself. Feb 3, 2017 at 3:07