
Concept explainers
Osteoporosis is an important cause of morbidity in middle- aged and elderly women. Several drugs are currently used to prevent fractures in postmenopausal women.
Suppose the incidence rate of fractures over a 4-year period is known to be 5% among untreated postmenopausal women with no previous fractures.
A pilot study conducted among 100 women without previous fractures aims to determine whether a new drug can prevent fractures. It is found that two of the women have developed fractures over a 4-vear period.
Suppose that 8 of the previous 100 women have developed abdominal pain during the trial, while only 1.5% would be expected to develop abdominal pain based on previous natural history studies.
Suppose the new drug is hypothesized to yield a frac-ture rate of 2.5% over a 4-year period. How many subjects need to be studied to have an 80% chance of detecting a significant difference between the incidence rate of fractures in treated women and the incidence rate of fractures in untreated women (assumed to be 5% from Problem 7.105)?

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Chapter 7 Solutions
Fundamentals of Biostatistics
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