Validation of a Short, 3-Item Version of the Subjective Numeracy Scale.

BACKGROUND AND OBJECTIVE: Efficiency in scale design reduces respondent burden. A brief but reliable measure of numeracy may provide a useful research tool eligible for integration into large epidemiological studies or clinical trials. Our goal was to validate a 3-item version of the Subjective Numeracy Scale (SNS-3).

DESIGN AND SETTING: We examined 7 separate cross-sectional data sets: patients in the emergency department (n = 208), clinic (n = 205), and hospital (n = 460; n = 2053) and patients with chronic kidney disease (n = 147), with diabetes (n = 318), and on hemodialysis (n = 143).

MEASUREMENTS: Internal reliability of the SNS-3 was assessed with Cronbach's α. Criterion validity was determined by nonparametric correlations of the SNS-3 with SNS-8 and other measures of numeracy; construct validity was determined by correlations with measures of health literacy and education.

RESULTS: The SNS-3 had good internal reliability (median Cronbach's α = 0.78) and correlated highly with the full SNS (median ρ = 0.91). The SNS-3 was significantly correlated with other measures of numeracy (e.g., median ρ = 0.57 with the Wide Range Achievement Test 4), health literacy (e.g., median ρ = 0.35 with the Shortened Test of Functional Health Literacy in Adults), and education (median ρ = 0.41), providing good evidence of criterion and construct validity.

CONCLUSION: The SNS-3 is sufficiently reliable and valid to be used as a measure of subjective numeracy.