STEM EVIDENCE WORKBENCH
Calculate signed percent change from the original magnitude and expose reversed direction, omitted decrease signs, denominator swaps, and arithmetic conflicts.
Review output
Load the worked example to inspect realistic inputs, or enter anonymous classroom or laboratory evidence. Results remain in this browser tab until you copy or download them.
Transparent method
Signed percent change equals (new minus original) divided by the absolute value of original, multiplied by 100. Absolute change is new minus original before division. The original magnitude is used so the sign continues to describe direction even in the bounded negative-baseline example. If original is zero, the ordinary formula is undefined. Swapping endpoints changes both the difference and denominator, so reverse changes are generally not equal opposites. Claim supported means the entered percentage matches the formula and sign convention. A direction flag means the magnitude agrees but the sign is reversed or omitted. A new-denominator flag means division by the new magnitude reproduces the response. These are visible arithmetic patterns, not diagnoses. Review what quantity forms the baseline, whether negative values make contextual sense, and whether the prompt instead asks for percentage points, percent difference, or an index.
Confirm the prompt, source values, units, signs, notation, precision, and model required by the current course. Keep an untouched copy of observations or responses before changing a row.
Run the worked example first, inspect every intermediate row, and compare the table with a hand calculation, diagram, number line, periodic table, or approved laboratory method.
Record the method, assumptions, units, rounding, limits, and any row that needs review. Use the exported report as editable evidence and verify it independently before assessment or laboratory use.
How to interpret the result
Use this diagnostic when learners confuse absolute difference, percent change, percent of a value, and percent difference. It is helpful after price, enrollment, measurement, or mathematical-change exercises where the baseline must stay explicit. The engine checks whether a wrong response matches the reversed sign, a new-value denominator, or an omitted decrease sign. It does not decide which percent convention a specialized discipline or policy requires.
The worked rows confirm an increase from 80 to 100 is positive 25% and a decrease from 50 to 40 is negative 20%. A move from 120 to 90 should be negative 25%, so an entered positive 25% is flagged for direction. A bounded example from -20 to -10 gives positive 50% under the stated signed-change-over-original-magnitude rule. The report keeps both endpoints beside expected and claimed percentages.
Signed percent change equals (new minus original) divided by the absolute value of original, multiplied by 100. Absolute change is new minus original before division. The original magnitude is used so the sign continues to describe direction even in the bounded negative-baseline example. If original is zero, the ordinary formula is undefined. Swapping endpoints changes both the difference and denominator, so reverse changes are generally not equal opposites.
Claim supported means the entered percentage matches the formula and sign convention. A direction flag means the magnitude agrees but the sign is reversed or omitted. A new-denominator flag means division by the new magnitude reproduces the response. These are visible arithmetic patterns, not diagnoses. Review what quantity forms the baseline, whether negative values make contextual sense, and whether the prompt instead asks for percentage points, percent difference, or an index.
Do not divide by the new value, remove the sign from a decrease without labeling an absolute percent decrease, confuse a change of 10 percentage points with 10%, calculate ordinary percent change from zero, or assume reversing a change restores the same percentage. Write original and new values, calculate signed difference, identify the baseline, estimate direction and size, attach units to the underlying quantities, and state the selected convention in the conclusion.
Learning boundary
This browser-local workbench applies only the disclosed rules to entered values. It cannot diagnose learning, establish a chemical structure, certify a measurement system, validate an experiment, or replace the method and judgment required by a teacher, curriculum, laboratory, or institution.
Review checklist
Practical questions
No. Processing occurs in the current browser tab. Avoid names and other personal information, and retain authoritative records only in the system approved by the school.
No. A matched pattern describes one entered response. Ask the learner to explain, use another representation, and review several evidence sources before deciding the next teaching step.
Treat it as an editable calculation aid. Show your own reasoning, use the method requested by the course, cite required sources, and follow the applicable academic-integrity rules.
YOUR NIRMION
