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Explore practical guides, step-by-step masterclasses, and foundational definitions across AI, SQL, and data systems — written in plain, human English.
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How to calculate a conversion rate correctly
Write conversion as success over eligible with a clear window. Definition cards beat dashboard magic when the same funnel stage means three rates.
Data warehouse, data lake, or plain database: which one does your data need?
App database, warehouse, or lake? Walk a plain decision tree for where data should live so product traffic, cheap history, and certified analytics stop fighting over one system.
How to pick an AI coding assistant like Claude Code or Codex, and use it well
For coding help, pick one AI surface, keep changes on one branch, list the folder, and re-run the failing command yourself. Agents multiply mistakes when nobody owns the…
Power BI for beginners: how to write measures that answer your question
Name Power BI measures after the question, write DAX that respects filter context, and test before the card goes live. Columns are raw material; measures are answers.
When to look at A/B test results and when to stop the test
Stop peeking at interim p-values as final decisions. Use fixed horizons or sequential plans, guardrail metrics, and a written stopping rule before launch.
