Which formula defines the Shannon diversity index, and what does a higher value indicate?

• A. H' = -sum(p_i log p_i); higher values indicate greater diversity.
• B. H' = sum(p_i^2); higher values indicate greater diversity.
• C. H' = log(sum p_i); higher values indicate lower diversity.
• D. H' = sum(p_i); higher values indicate greater richness.

Answer: (A)