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Verify calculations with executable evidence
Distinguish percentage-point change from relative change.
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Verify calculations with executable evidence
Distinguish percentage-point change from relative change.
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Source-based teaching example · Fictional data · Reviewed 2026-10-03. Microsoft Mark · locally synthesized. On a small screen, use fullscreen for diagram details or read the transcript.
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0:00 · What you will learn
Distinguish percentage-point change from relative change.
What appears on screen
Distinguish percentage-point change from relative change.
0:06 · The idea
Compare rates when groups have different totals. Name the measure you report. A numerical difference does not by itself prove what caused the change.
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Compare rates when groups have different totals. Name the measure you report. A numerical difference does not by itself prove what caused the change.
0:18 · One useful term
Percentage point. The direct difference between two percentages.
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The direct difference between two percentages.
0:26 · A worked example
Four errors in twenty tasks is twenty percent. Three errors in thirty is ten percent. The drop is ten percentage points, or a fifty percent relative reduction in the rate.
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Four errors in twenty tasks is twenty percent. Three errors in thirty is ten percent. The drop is ten percentage points, or a fifty percent relative reduction in the rate.
0:41 · Your turn to think
Does “ten percentage points” mean the same thing as “ten percent relative reduction”? Pause and decide before continuing.
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Does “ten percentage points” mean the same thing as “ten percent relative reduction”? Pause the video if you need more time.
1:00 · Why this answer works
No. The first subtracts rates; the second divides the change by the starting rate. These constructed counts do not prove causation.
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No. The first subtracts rates; the second divides the change by the starting rate. These constructed counts do not prove causation.
1:12 · Check 1
Check counts and the totals you divide by.
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Check counts and the totals you divide by.
1:17 · Check 2
Label the type of change.
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Label the type of change.
1:22 · Check 3
Do not assume tasks were equally difficult or that AI caused the change.
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Do not assume tasks were equally difficult or that AI caused the change.
1:29 · Now try a different case
Open the lesson and try its different practice case. Use every check in the full task. Watching alone does not mark the lesson complete.
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Open the lesson Try the new case Check and revise The full task and its requirements are in the linked lesson.
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