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

["Marlon Nelson" <marlon nelson gmail com>]

Thank you, Jean

Another question:  The data table was produced using the Histogram
tool.  The 1% bin counts 1011 data points between -1% and 1%.  In the
chart of the histogram, the area representing those points falls
between 1% and 3% on the x-axis.  Seems like an off-by-one problem to
me.

On Fri, Sep 12, 2008 at 11:17 AM, Jean Bréfort <jean brefort free fr> wrote:
> 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
>
>



-- 
-eom-