6.17 A research report states that ‘‘a comparison of 90 normal patients with
10 patients with hypotension shows that only 3.3% of the former group
died as compared to 30% of the latter.’’ Put the data into a 22 con-
tingency table and test the significance of blood pressure as a prognostic
sign using:
(a)Pearson’s chi-square test.
(b)Pearson’s chi-square test with Yates’s continuity correction.
(c)Fisher’s exact test.
6.18 In a trial of diabetic therapy, patients were either treated with phenfor-
min or a placebo. The numbers of patients and deaths from cardiovas-
cular causes are listed in Table E6.18. User Fisher’s exact test to investi-
gate the di¤erence in cardiovascular mortality between the phenformin
and placebo groups; state your null and alternative hypotheses.
TABLE E6.18
Result Phenformin Placebo Total
Cardiovascular deaths 26 2 28
Not deaths 178 62 240
Total 204 64 2686.19 In a seroepidemiologic survey of health workers representing a spectrum
of exposure to blood and patients with hepatitis B virus (HBV), it was
found that infection increased as a function of contact. Table E6.19
provides data for hospital workers with uniform socioeconomic status at
an urban teaching hospital in Boston, Massachusetts. Test to compare
the proportions of HBV infection between the four groups: physicians
with frequent exposure, physicians with infrequent exposure, nurses with
frequent exposure, and nurses with infrequent exposure. State clearly
your null and alternative hypotheses and choice of test size.
TABLE E6.19
Personnel Exposure n HBV Positive
Physicians Frequent 81 17
Infrequent 89 7
Nurses Frequent 104 22
Infrequent 126 116.20 It has been hypothesized that dietary fiber decreases the risk of colon
cancer, while meats and fats are thought to increase this risk. A large
study was undertaken to confirm these hypotheses (Graham et al., 1988).
Fiber and fat consumptions are classified as low or high and data are
240 COMPARISON OF POPULATION PROPORTIONS