Many types of medical decisions involve making sense of numbers such as test results, risk statistics, or prognosis estimates. But people vary in their ability and confidence with numbers. How would you rate your own "numeracy"?
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Not good at all
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Extremely good |
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How good are you at working with fractions? |
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How good are you at working with percentages? |
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How good are you at calculating a 15% tip? |
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How good are you at figuring out how much a shirt will cost if it is 25% off? |
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Not at all helpful |
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Extremely helpful |
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When reading the newspaper, how helpful do you find tables and graphs that are parts of a story? |
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Always prefer words |
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Always prefer numbers |
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When people tell you the chance of something happening, do you prefer that they use words ("it rarely happens") or numbers ("there's a 1% chance")? |
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Always prefer percentages |
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Always prefer words |
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When you hear a weather forecast, do you prefer predictions using percentages (e.g., "there will be a 20% chance of rain today") or predictions using only words (e.g., "there is a small chance of rain today") |
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Never |
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Very often |
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How often do you find numerical information to be useful? |
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Why is it important for researchers to know how numerate you are?
When a doctor or health educator is trying to communicate complex statistical information to a patient, it's helpful to know how well the patient understands numbers. This is called numeracy-the ability to process basic probability and numerical concepts. People low in numeracy might want or need different types of explanations than people high in numeracy.
How is numeracy measured?
In the past, researchers have used surveys similar to math tests to evaluate the levels of numeracy of participants in research studies. These objective numeracy tests can be time-consuming to administer and are often seen by the participants as stressful and annoying. As an alternative, a CBDSM research team-including Angela Fagerlin, Brian Zikmund-Fisher, Dylan Smith, Aleksandra Jankovic, and Peter Ubel-recently designed and tested an eight-item self-assessment tool, called the Subjective Numeracy Scale (SNS), to measure numeracy. As you saw when you completed the tool, four of the questions on the SNS measure people's beliefs about their skill in performing various mathematical operations, and four measure people's preferences about the presentation of numerical information. When the CBDSM team tested the SNS, they found that it was moderately correlated with objective numeracy tests. In a variety of risk communication and preference elicitation tasks, the SNS also predicted people's behavior almost as well as an objective numeracy test did. The advantage of the SNS is that it is quick to administer and is less stressful to participants than objective tests. In addition, only the SNS is recommended for phone or Internet administration. The researchers also found that study participants who completed the SNS were much more likely to answer all the numeracy questions and were much more likely to say that they would be willing to participate in an additional research study.
Are their broader implications?
Research has shown that many Americans, including highly educated individuals, have low levels of numeracy. Low numeracy has significant implications for people's health care, especially when it comes to understanding the risks and benefits of treatments. Although we may not easily change people's numeric ability, it may be possible to create health education materials that help patients with low numeracy skills. Several CBDSM researchers are have been pursuing this subject.
Read the articles:
Measuring numeracy without a math test: development of the subjective numeracy scale (SNS).
Fagerlin A, Zikmund-Fisher BJ, Ubel PA, Jankovic A, Derry HA, Smith DM. Medical Decision Making 2007;27(5):672-680.
Validation of the subjective numeracy scale (SNS): Effects of low numeracy on comprehension of risk communications and utility elicitations.
Zikmund-Fisher BJ, Smith DM, Ubel PA, Fagerlin A. Medical Decision Making 2007;27(5):663-671.
Making numbers matter: Present and future research in risk communication.
Fagerlin A, Ubel PA, Smith DM, Zikmund-Fisher BJ. American Journal of Health Behavior 2007;31(Suppl. 1):S47-S56.