how to calculate the slope of the least-squares regression line?
['Step 1: For each (x,y) point calculate x2 and xy.', 'Step 2: Sum all x, y, x2 and xy, which gives us Σx, Σy, Σx2 and Σxy (Σ means "sum up")', 'Step 3: Calculate Slope m:', 'm = N Σ(xy) − Σx Σy N Σ(x2) − (Σx)2', 'Step 4: Calculate Intercept b:', 'b = Σy − m Σx N.', 'Step 5: Assemble the equation of a line.']