How do I determine the class size for creating a histogram in statistics?

[Saladsamurai]

I have a quick question regarding a stats problem in my girlfriend's text. It is pretty easy I suppose, but I am not quite sure; the text does not appear to give a "general form" of how to obtain the info.

Feel free to correct me if I misuse words here, I am not familiar with the stats lingo yet.

It is asking to make a histogram. There is a table that gives us each state (the individual) and the number of Medical Doctors per 100,000 people is in each state (<--the variable, I presume).

Now I know that I find the Range by subtracting the Lowest Actual variable from the Highest actual Variable.

Here is where I am getting a little lost: I think now I am supposed to divide the actual range by the "class size" in order to find the number of classes so I can start to draw my histogram.

But how do I choose the size of each class? Is it arbitrary?

And why do I use the actuals to compute the range instead of the reasonable beginning/end?Thanks,
Casey

 

[EnumaElish]

I'd first plot the data by state to get a "feel."

Class size is arbitrary. It partly depends on whether you'd like the histogram to look like a "normal curve" or can live with "gaps in the middle."

You do not have to use the actual endpoints, but that's one way.