Missing-Data Field Cards
Recall when to drop, fill, flag, or investigate missing values in pandas.
flashcard-deck battlecard compare-card common-trap-callout What question should come before dropna? Ask whether the missing rows are rare, random, and irrelevant to the decision. Dropping is safest when it does not change the population being analyzed. Drop missing rows or flag missingness? Drop only when missingness is low-risk; flag when absence may carry segment or process meaning. When in doubt, flag first and decide after checking the pattern. Stakeholder says: just fill the blanks with zero so the chart is complete. Zero is a real value, not a synonym for unknown; I will use zero only if the source definition says…
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