Histogram normalised to area 1

Question

i have a histogram with the y-axis showing the proportion in percentage. That makes sense to me but now i have read that histograms can be normalized with the result that the area of the rectangles is 1.

Can someone explain me the idea,reason behind this? Many thanks!

Answer 1

Not all histograms are normalised.

For example, individuals by hair color:

• Blond 2 (Alex, Beckham)
• Gray 3 (Foo, Bar, Baz)
• ...

This histogram is not normalised, because individuals in result set are relevant.

Compare with repairs by car make:

• Fiat 81%
• Daewoo 18%
• Toyota 1%

This histogram is normalised to 100% because individual number of repairs is irrelevant.