It's not free, but https://www.amazon.com/Causal-Inference-Statistics-Biomedical-Sciences/dp/0521885884 https://www.amazon.com/Causal-Inference-Statistics-Biome

It's not free, but https://www.amazon.com/Causal-Inference-Statistics-Biomedical-Sciences/dp/0521885884 https://www.amazon.com/Causal-Inference-Statistics-Biomedica... is another excellent textbook for statistics.