I am regressing score(t)=b0 + b1score(t-1) + b2score(t-1)^2 + b3score(t-1)^3 where score(t-1) is previous score and score(t) is current score. I control for ethnicity, gender and year levels. I was expecting that b1 is positive to show that prior score predicts a positive relationship with current score. But my b1 is negative and b2 is positive and b3 is negative although the coeffcients are very small. How do I interepret b1 b2 and b3?  ... View more