Well, that doesn't exactly clear up the intended methodology. I'm kind of torn how to proceed, but I'm leaning toward my favorite "Quick and Dirty" solution to such problems, a spreadsheet!

If Y = Years since the beginning of the survey and S = Students:

Drawing a line, I get S(Y) = 24*Y+97.6

S(6) = 241.6

S(7) = 265.6

S(8) = 289.6

Strength: Simple.

Weakness: Data don't really suggest a linear relationship.

Weakness: Projections ONLY increase, EVER! That can't be right.

Weakness: Confusing NonInteger values. Just who is that 0.6 student?

Drawing a quadratic, I get S(Y) = 4.5714*Y<sup>2</sup> - 3.4286*Y + 129.6

S(6) = 273.6

S(7) = 329.6

S(8) = 394.7

Strength: Simple, but not as simple as linear.

Strength: Really NAILS the data.

Weakness: Projections ONLY increase, EVER, and WAY faster than the linear model. That REALLY can't be right.

Weakness: Confusing NonInteger values. Just who is that 0.7 student?

I really can't tell you how I arrived at these particular models. It was a normal mathematical procedure that is beyond the scope of your course. You may wish to use some averaging technique to create other equations,

-- Maybe use points 2 and 4 to define a unique line

-- Maybe use points 1, 3, and 5 to create a unique quadratic