Measuring numeracy without a math test: development of the Subjective Numeracy Scale.
BACKGROUND
Basic numeracy skills are necessary before patients can understand the risks of medical treatments. Previous research has used objective measures, similar to mathematics tests, to evaluate numeracy.


OBJECTIVE
To design a subjective measure (i.e., self-assessment) of quantitative ability that distinguishes low- and high-numerate individuals yet is less aversive, quicker to administer, and more usable for telephone and Internet surveys than existing numeracy measures.


METHODS
Paper-and-pencil questionnaires.


METHODS
The general public (N = 703) surveyed at 2 hospitals.


METHODS
Forty-nine subjective numeracy questions were compared to measures of objective numeracy.


RESULTS
An 8-item measure, the Subjective Numeracy Scale (SNS), was developed through several rounds of testing. Four items measure people's beliefs about their skill in performing various mathematical operations, and 4 measure people's preferences regarding the presentation of numerical information. The SNS was significantly correlated with Lipkus and others' objective numeracy scale (correlations: 0.63-0.68) yet was completed in less time (24 s/item v. 31 s/item, P < 0.05) and was perceived as less stressful (1.62 v. 2.69, P < 0.01) and less frustrating (1.92 v. 2.88, P < 0.01). Fifty percent of participants who completed the SNS volunteered to participate in another study, whereas only 8% of those who completed the Lipkus and others scale similarly volunteered (odds ratio = 11.00, 95% confidence interval = 2.14-56.65).


CONCLUSIONS
The SNS correlates well with mathematical test measures of objective numeracy but can be administered in less time and with less burden. In addition, it is much more likely to leave participants willing to participate in additional research and shows much lower rates of missing or incomplete data.
Fagerlin
Angela
A
VA Health Services Research & Development Center for Practice Management and Outcomes Research, VA Ann Arbor Healthcare System, Ann Arbor, Michigan, USA. fagerlin@med.umich.edu
Zikmund-Fisher
Brian J
BJ
Ubel
Peter A
PA
Jankovic
Aleksandra
A
Derry
Holly A
HA
Smith
Dylan M
DM
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D032882:Comprehension; D004521:Educational Measurement / Q000379:methods*; D005260:Female; D006787:Hospitals, Veterans; D006801:Humans; D008297:Male; D008433:Mathematics; D008875:Middle Aged; D010353:Patient Education as Topic; D010358:Patient Participation; D011795:Surveys and Questionnaires; D014481:United States