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ERIC Number: EJ881476
Record Type: Journal
Publication Date: 2009
Pages: 3
Abstractor: ERIC
Reference Count: 6
ISSN: ISSN-0002-7685
When the Numerator Is Zero: Another Lesson on Risk
Ho, Adrienne K.
American Biology Teacher, v71 n9 p531-533 Nov-Dec 2009
A biology teacher has developed a rare and troubling neurologic disorder. He hears of an experimental treatment that has produced impressive results. The treatment involves surgically ablating selective parts of the brain at close proximity to the brainstem. There is a risk that, during the procedure, vital parts of the brain could be inadvertently damaged and the patient could become paralyzed. He wants to know the risk estimation when the numerator is zero. Estimating the risk of a rare, but plausible, serious complication when none has yet occurred is an important concept. This article presents a lesson that involves problem solving and an activity on risk estimation. The article concludes that a zero numerator does not necessarily mean zero risk. It is possible to estimate the risk of a rare plausible complication even when it has not occurred, and when only the denominator is known. This is done through evaluating the likelihood of "n" successful trials for various confidence levels. The concept can be easily taught to non-mathematics students using a simple graph. (Contains 1 figure and 1 table.)
National Association of Biology Teachers. 12030 Sunrise Valley Drive # 110, Reston, VA 20191. Tel: 800-406-0775; Tel: 703-264-9696; Fax: 703-264-7778; e-mail:; Web site:
Publication Type: Journal Articles; Reports - Descriptive
Education Level: Higher Education
Audience: Teachers
Language: English
Sponsor: N/A
Authoring Institution: N/A