Average percentages with the right weight

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<p>Compare what happens when each group, each assignment, or each declared weight counts equally.</p>
<section class="results-three" aria-live="polite"><div><h2>Equal-row mean</h2><b id="equal">70%</b><span id="equalScope">2 available group rates</span></div><div><h2>Pooled count rate</h2><b id="pooled">83.333333%</b><span id="poolScope">10 / 12 assignments</span></div><div><h2>Custom weighted mean</h2><b id="weighted">76.666667%</b><span id="weightScope">Declared weights 2 : 1</span></div></section><p id="coverage" class="note" role="status">Incomplete coverage: G03 is missing; full three-group aggregate unavailable.</p>
<section class="panel below"><div class="fields"><label for="sourceMode">Source data<select id="sourceMode"><option value="counts">Completed / assigned counts</option><option value="rates">Percentages only</option></select></label><label for="basis">Common basis<input id="basis" value="Disjoint assignment groups · October 13, 2026"></label></div><div id="ledger" class="group-ledger"><section class="group-row"><h3>G01</h3><div class="count-fields fields"><label for="c0">Completed<input id="c0" inputmode="decimal" value="9" ></label><label for="n0">Assigned<input id="n0" inputmode="decimal" value="10" ></label></div><div class="rate-fields" hidden><label for="r0">Rate (%)<input id="r0" inputmode="decimal" value="90" ></label></div><label for="w0">Custom weight<input id="w0" inputmode="decimal" value="2" ></label><label for="reason0">If weight is 0, record why<input id="reason0" value=""></label><div id="rowState0" class="row-state"></div></section><section class="group-row"><h3>G02</h3><div class="count-fields fields"><label for="c1">Completed<input id="c1" inputmode="decimal" value="1" ></label><label for="n1">Assigned<input id="n1" inputmode="decimal" value="2" ></label></div><div class="rate-fields" hidden><label for="r1">Rate (%)<input id="r1" inputmode="decimal" value="50" ></label></div><label for="w1">Custom weight<input id="w1" inputmode="decimal" value="1" ></label><label for="reason1">If weight is 0, record why<input id="reason1" value=""></label><div id="rowState1" class="row-state"></div></section><section class="group-row"><h3>G03</h3><div class="count-fields fields"><label for="c2">Completed<input id="c2" inputmode="decimal" value="" ></label><label for="n2">Assigned<input id="n2" inputmode="decimal" value="" ></label></div><div class="rate-fields" hidden><label for="r2">Rate (%)<input id="r2" inputmode="decimal" value="" ></label></div><label for="w2">Custom weight<input id="w2" inputmode="decimal" value="" ></label><label for="reason2">If weight is 0, record why<input id="reason2" value=""></label><div id="rowState2" class="row-state"></div></section></div><label class="checklabel" for="comparable"><input type="checkbox" id="comparable" checked>Groups are disjoint and use the same assignment-count basis.</label><div class="actions"><button type="button" id="calculate">Recalculate</button><button type="button" id="reset" class="secondary">Reset example</button></div><p id="error" role="status" class="error"></p></section>
<section class="below panel"><h2>Calculation record</h2><p id="derive" class="formula"></p><p>Custom weights are separately declared; their real purpose and authorization need confirmation. Weighting by assigned counts reproduces the pooled rate. Percentages alone cannot reconstruct pooled counts.</p></section>
<details class="below"><summary>Missing data, zero weights, and limits</summary><p>Results always name their available-row scope. Missing G03 stays in the ledger. A 0/0 row is undefined; 0 completed with positive assigned is a defined 0%. In custom mode only, an explicit zero weight excludes a row with a recorded reason. Missing weights never become zero. A zero total weight has no weighted mean.</p><p>Counts must be integers with 0 ≤ completed ≤ assigned ≤ 1,000,000. Rate values accept 0–100%, up to six decimal places; weights accept nonnegative values up to 1,000,000 with six places. A partially entered or invalid row clears results. Final displays are rounded to six places from unrounded values. These fictional records are not staff or student results, grades, or policy. Entries are not saved.</p></details></main><script>
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function aggregate(rows,mode,comparable){let rates=[],valid=[],missing=[],undefinedRows=[],issues=[],weighted=[],weightMissing=[];rows.forEach((r,i)=>{const id='G0'+(i+1);let rate=null;if(mode==='counts'){if(r.c.trim()===''&&r.n.trim()===''){missing.push(id);}else{if(!/^\d+$/.test(r.c)||!/^\d+$/.test(r.n))throw Error(id+': enter both counts as nonnegative integers.');const c=Number(r.c),n=Number(r.n);if(c>n||n>1000000)throw Error(id+': require completed ≤ assigned ≤ 1,000,000.');if(n===0)undefinedRows.push(id);else{rate=c/n*100;valid.push({c,n,id});}}}else{if(r.r.trim()==='')missing.push(id);else rate=decimal(r.r,{max:100});}if(rate!==null)rates.push({rate,id});let w=null;if(r.w.trim()!=='')w=decimal(r.w);if(w===0){if(!r.reason.trim())throw Error(id+': a zero weight requires a reason.');issues.push(id+' excluded by declared zero weight: '+r.reason);}else if(rate!==null&&w!==null)weighted.push({rate,w,id});else weightMissing.push(id);});
return {equal:rates.length?rates.reduce((s,r)=>s+r.rate,0)/rates.length:null,pooled:mode==='counts'&&comparable&&valid.length?valid.reduce((s,r)=>s+r.c,0)/valid.reduce((s,r)=>s+r.n,0)*100:null,weighted:weighted.length?weighted.reduce((s,r)=>s+r.rate*r.w,0)/weighted.reduce((s,r)=>s+r.w,0):null,rates,valid,missing,undefinedRows,weightMissing,issues,weightedRows:weighted};}
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