Lab 07 / Communication
Points are not percent
Is a move from 4% to 6% a 2% or 50% increase?
Set a baseline and a new rate, then compare percentage points, relative change, and absolute counts side by side. Change one control at a time, then open the values under the chart before interpreting the picture.
View the values behind this chart
Loading the deterministic simulation...
SEEDInterpret the result
The paired guide explains the mechanism, assumptions, and cases where this display should not be generalized.
What this display answers
Percentage points subtract two rates directly. Relative percent change divides that difference by the baseline. Both can be correct, but they answer different questions.
Absolute counts add the denominator that either percentage can conceal. A two-point move has different practical scale in a population of 1,000 than in 100,000.
What to notice
- Start at 4% and 6%: the result is +2 percentage points and +50% relative change.
- Set the baseline to zero. The point change still exists, but relative change is undefined.
- Change only the reference count. Rates stay fixed while the count difference changes.
The model behind it
Rates are entered on a 0-100 percent scale and applied to one fixed synthetic reference count.
The controls use whole percentages and reference populations divisible by 100, so displayed expected counts are whole numbers. They are model outputs, not observed people.
Where the result stops
Relative changes around a very small baseline can sound dramatic while representing a small absolute difference.
Always state the denominator, time window, and whether a reported percent means rate, share, or relative change.