Hi,

I would like to compare two batches of a product over time to see if they behave similarly, i.e same slope and intercept. This is a stability study. I will be performing ANCOVA analysis for this. According to ICH and FDA guidelines, if the test rejects the hypothesis of equality of slopes, then I should fit a regression line to each batch where the intercept and the slope are the individual ones but I should use the pooled mean square error calculated from all batches.

I wonder if anyone could help me to feed the calculated pooled mean square error in the function lm() or if there is another way to perform such analysis. 

Thanks for your help,

Dave
 		 	   		  
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