How do I cite my own work?
It is a different format than the previous paper but it is on the same subject
Answer
APA is designed for professionals publishing in the professional literature, and so we probably are not going to find a rule for citing a class paper.
Therefore, we need to look to the "spirit" of APA and not the letter to figure this one out.
I would say yes, if you are paraphrasing your earlier or work or directly quoting something you wrote from a previous paper then that does need to be explained to the reader.
I would treat the previous paper you are citing as an unpublished manuscript, since the reader will not be able to use any traditional information sources to locate a copy of your paper (i.e. it is not published, therefore not available through a library or commercial source). Here is how APA cites an unpublished manuscript, from p. 211 of the Publication Manual of the American Psychological Association, 6th ed. -
Author, A . A. (Year). Title of manuscript. Unpublished manuscript.
An example -
White, T. (2012). What I did on my Christmas vacation. Unpublished manuscript.
Or, we might be able to tweak the unpublished doctoral dissertation or master's thesis (p. 207 of the Publication of the American Psychological Association, 6th ed.).
Author, A. A. (Year). Title of doctoral dissertation or master's thesis (Unpublished doctoral dissertation of master's thesis). Name of Institution. Location.
An example -
White, T. (2012). What I did on my Christmas vacation. (Unpublished class paper). The College of St. Scholasatica.
Duluth, MN.
_________________________
Looking at the two examples I created, I would go with the second. It gives author, date & title, and explains what the document is. "Unpublished" might be redundant, since it is a class paper, but I think I would leave it in.
Hope this helps, and hope you are off to a good new year.