Why would using all six characters of the POSTCODE attribute be suboptimal?

• A. It would generate many groups, each with a small number of features.
• B. It would generate few groups, each with a large number of features.
• C. It would generate few groups, each with a small number of features.
• D. It would generate many groups, each with a large number of features.

Answer: (A)

Granularity of grouping by an attribute affects both performance and the usefulness of the results. If you use all six characters of the POSTCODE for grouping, you create a very large number of distinct groups because postcodes are typically unique at that level. Many groups will end up with only a few features each, sometimes just one. This fragmentation increases the overhead of managing groups (more group buckets, more memory and processing time) and reduces the statistical value of each group, since with so little data per group the results become noisy and less reliable. In contrast, a coarser grouping (fewer characters or a broader attribute) yields fewer groups with more features per group, improving processing efficiency and the meaningfulness of any per-group calculations.