(a)For each of the two factors (duration of unprotected intercourse and
history of infertility, treating the latter as ordinal: no history, history
but no drug use, and history with drug use), choose the lowest level
as the baseline, and calculate the odds ratio associated with each
other level.
(b)For each of the two factors (duration of unprotected intercourse and
history of infertility, treating the latter as ordinal: no history, history
but no drug use, and history with drug use), calculate the generalized
odds and give your interpretation. How does this result compare
with those in part (a)?1.27 Postneonatal mortality due to respiratory illnesses is known to be
inversely related to maternal age, but the role of young motherhood as a
risk factor for respiratory morbidity in infants has not been explored
thoroughly. A study was conducted in Tucson, Arizona, aimed at the
incidence of lower respiratory tract illnesses during the first year of life.
In this study, over 1200 infants were enrolled at birth between 1980 and
- The data shown in Table E1.27 are concerned with wheezing lower
respiratory tract illnesses (wheezing LRI: no/yes).
TABLE E1.27
Boys Girls
Maternal Age (years) No Yes No Yes
< 21 19 8 20 7
21–25 98 40 128 36
26–30 160 45 148 42
> 30 110 20 116 25(a)For each of the two groups, boys and girls, choose the lowest age
group as the baseline and calculate the odds ratio associated with
each age group.
(b)For each of the two groups, boys and girls, calculate the generalized
odds and give your interpretation. How does this result compare
with those in part (a)?
(c)Compare the two generalized odds in part (b) and draw your con-
clusion.1.28 An important characteristic of glaucoma, an eye disease, is the presence
of classical visual field loss. Tonometry is a common form of glaucoma
screening, whereas, for example, an eye is classified as positive if it has
an intraocular pressure of 21 mmHg or higher at a single reading. Given
the data shown in Table E1.28, calculate the sensitivity and specificity of
this screening test.
46 DESCRIPTIVE METHODS FOR CATEGORICAL DATA