19.9 Hiearchical model

• Just as different expeditions have related climber success probabilities, we expect the same for different peaks.

• We don’t really care about the particular subset of peaks in the data, but we want to incorporate it -> Grouping variable.

• Now we have two ‘tweaks’, $b_{0j}$ adjustment for expedition j and $p_{0k}$, adjustment for peak k.

• $Y_{ijk}$ is the success of the i’th climber, who climbed the j’th peak in the k’th expedition. (nested structure of the data)

• $\sigma_b$ is the variability of success rates from expedition to expedition (within a peak)

• $\sigma_p$ is the variability between peaks.