ANCOVA (Analysis of Covariance): A Mix of ANOVA and Regression

Thankful to you! what a fabulous way of teaching.

How would I use ANCOVA to determine if a common slope can be used for degradation of active ingredient in drug product? I have 3 batches tested at 0, 3, 6, 9, 12, 18 and 24 months. What would be the covariate?

Thank you very much...

Are you planning to publish a course? Is this covered in your book?

Splendid.
Thank you for sharing this, you don't know how much obstacles we do face in limited resources country to study and understand Biostatistic.