Re: Histogram chart - What do the y-axis numbers mean?

[Jean Bréfort <jean brefort free fr>]

Le vendredi 12 septembre 2008 à 10:46 -0400, Marlon Nelson a écrit :
> I originally thought this was a bug and was about 30 seconds from
> submitting one to bugzilla when I began to suspect the problem is with
> my understanding of what a histogram is.
>
> With the data listed below (frequency of daily returns of Merrill
> Lynch stock over the last 10 years), I created a histogram chart.  The
> highest point on the chart reaches 50,000.  I was expecting 1011.
>
> Reading a bit from wikipedia, I see what I was actually expecting to
> see is a bar chart.
>
> But given a histogram chart of this data, what do the y-axis numbers mean?
>
> Bin   Frequency
> -15%  1
> -13%  1
> -11%  4
> -9%   6
> -7%   13
> -5%   53
> -3%   167
> -1%   510
> 1%    1011
> 3%    489
> 5%    156
> 7%    57
> 9%    26
> 11%   6
> 13%   4
> 15%   3
> 17%   2
>
> --
> -eom-

The histogram plots the density, as the 1011 data are in a 0.02
interval, you get 1011 / 0.02 = 50550 as the largest value.

Regards,
Jean