PUBH 6333 Week 6 Risk Numbers Memo Example

Memorandum

To: Injury Prevention Program Manager, Pruett County Health Department

From: Health Communication Intern

Date: Month Day, Year

Re: Revising four figures in the mower campaign drafts before the second pretest round

Purpose

Numbers in a health message are often the part no one checks for understanding, because they look precise. The first pretest round showed that men read our figures confidently and wrongly. This memo audits all four figures in the draft materials and recommends a revision for each. A systematic review of how to communicate probabilities found that absolute numbers support more accurate understanding than relative ones, and that how figures are presented changes what people decide (Zipkin et al., 2014).

Figure 1: "Kids who ride are far more likely to be hurt."

The radio draft says children who ride on mowers are "far more likely" to be hurt. This is a relative claim with no number and no baseline. More likely than what? Children who never go near a mower? Children in the yard during mowing? Two pretest participants took it to mean that riding is dangerous but standing nearby is fine, the reverse of the evidence. In the survey of families of seriously injured children, bystanders were 69% of those injured and riders 24%, and 73% of injured bystanders had been given rides before (Jennissen et al., 2023). The point is not that riders are more often hurt; it is that rides lead children toward running mowers later.

Revision: "Most children badly hurt by riding mowers were not riding. They ran toward a mower they had ridden before."

Figure 2: "59% of injuries happen in reverse."

The counter card says 59% of mower injuries to children happen when the mower is backing up. The number is accurate for a specific group: families of seriously injured children who answered one survey (Jennissen et al., 2023). It is not a national figure for all mower injuries, most of which are cuts and burns treated and released from emergency departments (Vollman & Smith, 2006). Three participants read "59%" as "about half of all mowing accidents," and one asked, "Out of what?" The reference class is never named.

Revision: "In one study of children who lost a foot or were badly hurt, most were hit while the mower was backing up." This drops the exact percentage, names the group and keeps the action that matters.

Figure 3: "9,400 kids a year."

The tag draft says "9,400 kids a year are hurt by mowers." The figure is an average of U.S. emergency department visits from 1990 to 2004 for young people aged 20 and under, not only small children, and it is more than twenty years old (Vollman & Smith, 2006). Several participants doubted it ("That many?") or thought it meant deaths. A national number also feels distant in a county of 40,000.

Revision: remove the figure from the tag, which has room for only one idea. On the counter card, write: "Every year, emergency rooms across the country see thousands of children and teens hurt by mowers." Keep the exact figure, with its years and age range, on the web page.

Figure 4: The Heat-of-the-Moment Number

The radio draft ends, "It only takes a second." This is a phrase, not a statistic, but men read it as a probability claim and rejected it: "I'd see him in a second." The phrase invites a reader to test his reflexes against it.

Revision: replace with an instruction that does not depend on speed: "Before you back up, stop and look."

A Rule for Future Figures

Every number the campaign uses should answer three questions in plain words: who is counted, during which years and against which comparison. Where a number cannot answer all three on a small piece, it should be moved to a place that has room, or replaced with a natural frequency, such as "out of every 10 children," which people find easier to reason with than percentages (Gigerenzer, 2011).

Recommendation

Adopt the four revisions for Round 2 of the pretest and add a probe asking participants what each remaining number means. Fewer numbers, each clearly bounded, will serve men like Dale better than more numbers that sound authoritative.

References

Gigerenzer, G. (2011). What are natural frequencies? BMJ, 343, Article d6386. https://doi.org/10.1136/bmj.d6386

Jennissen, C. A., Krupp, T. D., Vakkalanka, J. P., & Hoogerwerf, P. J. (2023). Pediatric lawn mower-related injuries and contributing factors for bystander injuries. Injury Epidemiology, 10(Suppl. 1), Article 51. https://doi.org/10.1186/s40621-023-00468-z

Vollman, D., & Smith, G. A. (2006). Epidemiology of lawn mower-related injuries to children in the United States, 1990-2004. Pediatrics, 118(2), e273-e278. https://doi.org/10.1542/peds.2006-0056

Zipkin, D. A., Umscheid, C. A., Keating, N. L., Allen, E., Aung, K., Beyth, R., Kaatz, S., Mann, D. M., Sussman, J. B., Korenstein, D., Schardt, C., Nagi, A., Sloane, R., & Feldstein, D. A. (2014). Evidence-based risk communication: A systematic review. Annals of Internal Medicine, 161(4), 270-280. https://doi.org/10.7326/M14-0295