Scenario 2: The Mayor’s Press Conference

Scenario 2: The Mayor’s Press Conference

A city in northern Georgia has been under pressure to improve air quality after several years of exceeding EPA safety limits for fine particulate matter (PM2.5 — tiny particles that can penetrate deep into the lungs). The EPA limit is 35 µg/m3. After investing $4 million in new emissions controls, the city releases the following data:

  • 2019 average PM2.5: (42 ± 15) µg/m3
  • 2024 average PM2.5: (38 ± 12) µg/m3

At a press conference, the mayor declares: “Our investment is working. Air quality has measurably improved and our residents are breathing cleaner air.”

A local environmental advocacy group responds: “The data does not support that claim.”

Discussion questions:

  1. What does the ± value represent in each measurement? What does it mean for the range of possible true values?
  2. Do the 2019 and 2024 measurements actually differ in a meaningful way given their uncertainties? Show your reasoning.
  3. Is either measurement consistent with being at or below the EPA safety limit of 35 µg/m3? Explain.
  4. Who do you think is making the stronger argument — the mayor or the advocacy group? Why?
  5. What would the data need to look like for the mayor’s claim to be defensible?
  6. What are the consequences of overstating or understating what this data shows — for residents, for policy, for public trust in science?