Ahh, thanks for the help. It works perfectly.
To answer your question, I have to graph lab data on the photosynthetic rates of leaf discs in different solutions and after a certain amount of time the leaf discs in one solution are floating while in another, they still are not floating(We were too take measurements until all of the discs floated). The Prof. instructed us to use only the values that are apart of the actual slope when calculating the trendline(I dont know too much about statistics so I took her word on it).
Oh yeah, this lab is lame.