{"id":"fpa-purchase-price-usage-variance","audience":"fpa","category":"finance-work","track":"finance","technique":"verification","level":"intermediate","title":"Split a materials variance into price and usage","free":false,"task":"You're explaining a materials cost variance for the month. Write a prompt for plain text with lines starting \"Price variance:\", \"Usage variance:\", \"Total variance:\" and \"Check:\", each with the math. Price variance = (actual price - standard price) x actual quantity. Usage variance = (actual quantity - standard quantity allowed) x standard price. Positive means unfavorable. Don't state causes or blame a supplier. Under 80 words. No bullets or numbering.","materialLabel":"Standard and actual materials data (attached to your prompt automatically)","material":"MATERIALS VARIANCE INPUTS - October 2026, packaging resin\n\nStandard price: $12.00 per kg\nActual price paid: $12.60 per kg\nStandard quantity allowed for October output: 4,800 kg\nActual quantity used: 5,000 kg\n\nSign convention: a positive variance is unfavorable (costs more than standard).\n\nComments: purchasing says the supplier raised prices without notice; production says the extra 200 kg was scrap from a machine jam. Neither explanation has been checked. The requested analysis is the arithmetic only.\n\nBackground: the standard price was set in January from the supplier's quote. Output last month was 2,400 units, and the standard quantity allowed is 2 kg per unit, which is how the 4,800 kg figure arises. The plant controller reviews these variances monthly and sends the result to the COO. Resin is purchased on 30-day terms.","rules":[{"type":"plainText"},{"type":"maxWords","max":80},{"type":"maxBullets","max":0}],"promptHints":[{"label":"Names the four lines","patterns":["price variance","usage variance","total variance","check:"]},{"label":"Gives the formulas","patterns":["actual price - standard","actual quantity - standard"]},{"label":"Asks for the check","patterns":["actual cost","standard cost"]},{"label":"Bans causes","patterns":["(do not|don'?t).*(cause|supplier)"]},{"label":"Caps length","patterns":["\\d+\\s*words","plain"]}],"mistakes":[{"title":"Using the wrong bases","why":"The AI uses standard quantity for the price variance.","fix":"Say: \"Price variance uses actual quantity; usage variance uses standard price.\"","checks":["r0"]},{"title":"Repeating the explanations","why":"The AI says the supplier raised prices and scrap caused the usage.","fix":"Add: \"Do not give causes or mention suppliers, scrap or machines.\"","checks":["r2"]},{"title":"No check","why":"The AI never ties the split back to total cost.","fix":"Add: \"Check: actual cost minus standard cost.\"","checks":["r2"]},{"title":"Markdown extras","why":"The AI adds bold labels, headings and a closing note.","fix":"Say: \"Plain text, no bold. Output only the lines asked for.\"","checks":["plainText","maxBullets","r1"]},{"title":"Trusting the AI to count words","why":"AI is bad at counting and runs past word limits.","fix":"Ask for fewer words than the real cap and keep each line short.","checks":["maxWords"]}],"hint":"The two variances use different bases. Give both formulas, the sign convention and a ban on causes.","rubricLabels":["The line starting \"Price variance:\" shows ($12.60 - $12.00) x 5,000 = +$3,000 unfavorable and the line starting \"Usage variance:\" shows (5,000 - 4,800) x $12.00 = +$2,400 unfavorable","The line starting \"Total variance:\" shows $3,000 + $2,400 = +$5,400","The line starting \"Check:\" shows actual cost $63,000 - standard cost $57,600 = $5,400, and the output never mentions the supplier, the scrap or the machine jam"]}