Fisher-Irwin test

Multiple Pairwise Group Comparisons by Fisher-Irwin Exact Test... 

Requirements for nongrowing adults are based on a limited number of depletion-repletion studies carried out on small numbers of subjects. These studies have been reviewed by Rodriguez and Irwin (1972). An abnormal dark adaptation was the criterion used to determine an inadequate vitamin A status in the early studies. This test provided no measure of the body pool size of vitamin A when abnormal dark adaptation occurred. Dark adaptation in adults is known to be affected by factors other than vitamin A (Fisher et al., 1970 Ripps, 1982). Thus it was difficult, even in the classic Sheffield depletion study of the British Medical Research Council (Hume and Krebs, 1949), to attribute aberrant dark adaptation specifically to the relative vitamin A status of subjects. This was particularly true because there was a poor correlation between blood levels of vitamin A and evidence of impaired dark adaptation until blood levels fell critically low and clinical signs became obvious. It is therefore most unfortunate that a carefully controlled study of adult human requirements that used labeled retinol has not been fully reported (Hodges and Kolder, 1971). From the data available (Sauberlich et al., 1974), individual variation in blood and clinical responses to... 

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