15.1 Use refreshers when the project needs them

Applied projects require knowledge from several technical areas. A refresher should reactivate a concept and connect it to the current decision. It should not become an excuse to repeat every topic from an earlier statistics, programming, spreadsheet, or machine-learning text.

Before reviewing a topic, identify the project need. For example:

• “We need conditional proportions to compare retention across acquisition channels.”
• “We need grouped time summaries to create facility-level monthly series.”
• “We need absolute spreadsheet references so one discount-rate assumption is used consistently.”
• “We need a star schema so visit measures filter correctly by centre and date.”

This approach keeps technical review purposeful.