Everyone’s talking about “AI-based” media mix modeling. There’s a lot of hype in the space – but what’s real and what’s not? From our experience, there’s a fundamental mismatch between what large language models (LLMs) do and what MMMs require.  LLMs like ChatGPT are optimized for one thing: predicting the next word in a sequence. MMMs, by contrast, estimate causal relationships over time. They’re solving completely different mathematical problems, and expecting one to perform the other’s job is a category error. LLMs don’t learn from data in the way that statistical models do. When you use an LLM, the weights of the neural network do not change. They are just being pushed through the network to generate tokens. In contrast,…