An empirical comparison of how fertility patients and health care professionals interpret verbal probability expressions.

OBJECTIVES

To investigate how fertility patients (FPs) and healthcare professionals (HCPs) interpret verbal probability expressions used to communicate the chance of pregnancy with fertility treatments, and whether patient-professional group membership accounts for a meaningful proportion of the observed variation.

METHODS

Participants completed two online judgment tasks in a generalized fertility treatment context. In the ordering task, they ranked 16 probability terms from highest to lowest perceived chance of pregnancy. In the rating task, they assigned numerical probabilities (0-100%) to each term. Data quality was assessed using Kendall's τ; reversed orderings were corrected and disengaged responses excluded. Between-group differences of the ordering task were tested using log-linear models with permutation tests. Rating distributions were compared using Kolmogorov-Smirnov tests with permutation correction. Analysis of variance estimated the proportion of variance explained by group membership versus within-group variability. Consistency between tasks was assessed using Kendall's τ.

RESULTS

After quality exclusions, 163 FPs and 129 HCPs contributed ordering data; 135 FPs and 102 HCPs contributed rating data. Rankings and ratings were broadly intuitive, with extreme terms (e.g., "almost no chance") eliciting greater consensus than mid-range terms (e.g., "likely"). Distributions differed significantly between FPs and HCPs, with FPs generally assigning higher probabilities. However, between-group differences accounted for a small proportion of variance (ordering: median 1.20%; rating: median 3.00%), indicating most interpretive variability occurred within groups. Ordering and rating responses were strongly correlated within individuals in both groups (τ ≈ 0.77).

CONCLUSION

Verbal probability expressions in fertility care are interpreted heterogeneously. Within-group variation outweighed differences between FPs and HCPs, indicating that group membership accounted for little of the observed variation; the design cannot identify the sources of the remaining variation.

PRACTICE IMPLICATIONS: Clinicians should avoid relying solely on verbal probability terms and instead combine them with explicit numerical ranges and clarification strategies to support informed decision-making and shared understanding.