Missing Data — Prelims Strategy

Prelims Strategy

Label blank entries with variables and identify what the question asks for before solving. Translate row totals, column totals, averages and ratios into equations with consistent units. Convert an average into a total using the correct number of observations, and attach each percentage to its stated denominator.

Check whether the conditions are independent. Multiplying an existing equation by two does not add information. If the unknown entries cannot be individually recovered, test whether the requested sum or difference is nevertheless fixed. A pair of valid assignments producing different answers demonstrates insufficiency more clearly than an unfinished calculation.

Use domain restrictions only when justified: a number of people must be an integer, but an average age need not be. Treat rounded percentages with the precision given rather than as exact fractions by default. Substitute the recovered values into every supplied total and look for inconsistencies. Finally, reject the temptation to continue an apparent numerical sequence unless the question explicitly establishes that the entries follow such a rule.