The relationship between prior condom use and tubal pregnancy was assessed in a population-based case-control study at Group Health Cooperative of Puget Sound during 1981-1986. The results are shown in Table E1.3. Compute the group size and the proportion of subjects in each group who never used condoms.
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TABLE E1.3
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Condom Use
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Cases
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Controls
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Never
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176
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488
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Ever
|
51
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186
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