Step 1: Understand authority in informal organizations.
In informal organizations, authority is not centralized but decentralized, meaning decision-making is shared among individuals based on personal relationships, expertise, and trust rather than formal chains of command.
Step 2: Evaluate the options.
- In informal organizations, authority is decentralized and informal, with influence spread across different individuals depending on their roles and relationships.
Step 3: Conclude.
The correct answer is decentralized.
Final Answer:
\[
\boxed{\text{Decentralised}}
\]