Jiawen Liu, Jacky Boivin, Rebecca Lewton, Joanna Woolner, Richard D Morey
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.
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 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.