i don't have any stats books with me because i am not at home so i was hoping someone could direct me to a book or maybe there is a way to do it in R ? i do an lm with no intercept and there are 6 coeeficients on the right hand side and i get back estimates of model which is fine in the sense tha i check the t-stats and do normality, indepenendence of residual checks etc. then, some more data points come in ( say 20 ) and i use the coeeficients that i estimated previously to calculate the residuals ( the new residuals and the previous residuals ). what i want are the t-stats on the old regression coefficients ( really just the first one actually )to see if they are still significant, given the new data, but i'm not reestimating. i still want to use the previous coeeficients. is there a formula for this or a way to do this in R ? thanks.