+1}{2}\\
s_{TW} & = n \times \frac{s_1 + \ldots + s_n}{n},\end{aligned}$$ where the slope is a result of straightforward differentiation .

This model yields much better results than other models; note, however, that the absence of false observations is a strong requirement. Other models have to operate without this assumption. Note that the $P_{TW}(c)$ is not normal.

Aggregation of information in hierarchical schemes {#s:aggregation}
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So far, we have assumed that information from all participants is simultaneously collected and used in the group decision. One may argue that this is unrealistic for human communication in groups of more than a few persons. We, therefore, propose hierarchical models (schemes) in which only small subgroups can communicate at a particular time. Each of these subgroups reaches its own decision, in a manner described by one of the models introduced in the previous section. Hence, the subgroup can be regarded as a decision-making agent, described by a slope and a bias. The subgroup can then communicate with other subgroups or individual members, which results in larger groups being created, until all information is gathered and the final decision is made.

The results of employing a multi-level decision system can significantly deviate from what 