Sampling●Shala
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Learn sampling, one honest idea at a time

Every explainer below opens with a definition you can quote, then the formula, a visual, and a worked example from real education fieldwork. When an idea clicks, the live playgrounds in Learn mode let you push its sliders yourself; the full in-app library covers 42 concepts across six themes.

Stratified samplingDivide, then sample within every group, so no one is left to chance. Cluster samplingSample whole schools, pay the design effect. The workhorse of field surveys. Confidence intervalYour estimate as a range, and what 95 percent actually promises. Margin of errorThe plus-or-minus band, and why halving it quadruples the sample.

For evaluation teams

Sample size for program evaluationEight designs, one honest engine. How many schools to survey?From design effect to school count. LQAS explained19 children per block, one pass-or-flag rule. Sample size calculatorThe free tool behind these pages.

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