Calculate mean deviation of the mean

[#1]

I'm a beginner in statistics and JMP.

I have a column with text lengths. I managed to calculate the mean text length. But now I need to calculate the mean deviation of the mean text length.

Is this the same as the standard deviation of the column with text lengths or is this another calculation? And how do I do it in JMP?

Thank you for your help.

[#2 · Accepted solution]

My suggestion would be that you take that new column, which contains the text length for the entry for the column, and then run 

     Analyze==>Distribution 

on the new column.  It will provide you with the Mean, STD, STD Error of the Mean, etc.

[#3]

And is the standard deviation of that column with text lengths then the same as the mean deviation of the mean text length?

I don't get the concept 'mean deviation of the mean' entirely.

[#4]

The standard deviation is different than the mean deviation.  The mean deviation is simply taking the the average of the absolute value of the mean subtracted from each value.

use

If you created a new column and used the following formula

     abs(:text length - col mean(:text length))

and then run the Distribution on that new column, the displayed mean would be the Mean Deviation

[#5]

Ok, I understand.

Last question, is the standard deviation of the mean text length yet another calculation or is that just the S.D. of the column with text lengths?

Thanks!