add conclusion section

docs/source/notebooks/mmm/mmm_roas.ipynb

@@ -1285,6 +1285,15 @@
     "The estimates are very very close to the true ROAS! We do get from the model that `x1` is more effective than `x2`, which is aligned with the lift test results!"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Conclusion\n",
+    "\n",
+    "In this notebook, we have shown that the PyMC-Marketing approach of adding lift test measurements to the model is very similar to the one proposed in the paper [Media Mix Model Calibration With Bayesian Priors](https://research.google/pubs/media-mix-model-calibration-with-bayesian-priors/) and the blog post [Media Mix Model and Experimental Calibration: A Simulation Study](https://juanitorduz.github.io/mmm_roas/). However, the PyMC-Marketing approach is more flexible as it allows to enrich the estimates with more lift test and different media spends to have a better understanding of the saturation effect. We have also seen why it is important to include the lift test measurements in the model to account for the unobserved confounders and to have a better understanding of the saturation effect."
+   ]
+  },
   {
    "cell_type": "code",
    "execution_count": 23,