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Biostatistics

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738 CHAPTER 13 NONPARAMETRIC AND DISTRIBUTION-FREE STATISTICS<br />

(c) Formulate relevant hypotheses, perform the appropriate tests, and find p values.<br />

(d) State the statistical decisions and clinical conclusions that the results of your hypothesis tests<br />

justify.<br />

(e) Describe the population(s) to which you think your inferences are applicable.<br />

(f) State the assumptions necessary for the validity of your analyses.<br />

15. The purpose of a study by Damm et al. (A-17) was to investigate insulin sensitivity and insulin<br />

secretion in women with previous gestational diabetes (GDM). Subjects were 12 normal-weight<br />

glucose-tolerant women (mean age, 36.6 years; standard deviation, 4.16) with previous gestational<br />

diabetes and 11 controls (mean age, 35 years; standard deviation, 3.3). Among the data collected<br />

were the following fasting plasma insulin values (mmol/L). Use the Mann–Whitney test to determine<br />

if you can conclude on the basis of these data that the two populations represented differ with respect<br />

to average fasting plasma insulin level.<br />

Controls Previous GDM Controls Previous GDM<br />

46.25 30.00 40.00 31.25<br />

40.00 41.25 30.00 56.25<br />

31.25 56.25 51.25 61.25<br />

38.75 45.00 32.50 50.00<br />

41.25 46.25 43.75 53.75<br />

38.75 46.25 62.50<br />

Source: Data provided courtesy of Dr. Peter Damm.<br />

16. Gutin et al. (A-18) compared three measures of body composition, including dual-energy x-ray<br />

absorptiometry (DXA). Subjects were apparently healthy children (21 boys and 22 girls) between the<br />

ages of 9 and 11 years. Among the data collected were the following measurements of bodycomposition<br />

compartments by DXA. The investigators were interested in the correlation between all<br />

possible pairs of these variables.<br />

Percent Fat<br />

Fat Mass<br />

Fat-Free<br />

Mass<br />

Bone<br />

Mineral<br />

Content<br />

Fat-Free<br />

Soft<br />

Tissue<br />

11.35 3.8314 29.9440 1.19745 28.7465<br />

22.90 6.4398 21.6805 0.79250 20.8880<br />

12.70 4.0072 27.6290 0.95620 26.6728<br />

42.20 24.0329 32.9164 1.45740 31.4590<br />

24.85 9.4303 28.5009 1.32505 27.1758<br />

26.25 9.4292 26.4344 1.17412 25.2603<br />

23.80 8.4171 26.9938 1.11230 25.8815<br />

37.40 20.2313 33.8573 1.40790 32.4494<br />

14.00 3.9892 24.4939 0.95505 23.5388<br />

19.35 7.2981 30.3707 1.45545 28.9153<br />

29.35 11.1863 26.8933 1.17775 25.7156<br />

(Continued)

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