In the Boxplot procedure, the SYMBOL statement has very little control over the mean representation, and none over the boxes themselves. When you specify INTERPOL=BOX10 -- it is simply ignored. Only the V and colors options are considered for drawing the boxplot. You can change the boxplots color with the CBOXES option in the PLOT statement.
idsymbol = dot CBOXES=BLACK
The SYMBOL statement has only effect on the point that represent the means. So you can change the symbol itself (V=), its color (C=), but cannot connect them, for example, with I=JOIN. That was what I meant in my post. If you delete the I=BOX10 in your program, I think that your boxplots are generated just the same, aren't they ?
I retried it and your right whether i had the interpol in there or not or even as a different value the graphs were the same. I find that unusual since all of the examples I've seen online are like that too yet supposedly they worked and even in the SAS/graph manual it says to add that in the symbol statement. So I am assuming that this needs to be specified in the same area I just added cboxes, but what termination can I use? I tried both i= and interpol= and neither seem to work. Thank you for all of your help.
In fact, there are 2 different ways to draw boxplots in SAS : 1) in a GPLOT procedure, with SYMBOL INTERPOL=BOX (this is the "old" way) ; 2) in a BOXPLOT procedure, where SYMBOL rules over a lot less options on the graph (the Boxplot proc was introduced in sas 8.0, if I remember well).
So if you run a Boxplot proc without any Symbol statement, the mean is showed as a black plus (+) sign (= the default). If you want to connect these means, you don't use SYMBOL INTERPOL=JOIN, but an option in the Boxplot proc.