Basic Statistics

PROBLEMS 163

(c) Compute chi-square and test that the proportion of smokers is the same

among cases and controls for (a) and (b). Is the chi-square the same if the

number of controls is doubled?

11.3 A matched sample casekontrol study was performed using cases and controls
who have been matched on age and eye color and who all worked for the
same chemical company. The cases had been diagnosed with melanoma. The
exposure factor being studied was exposure to a chemical. The number of pairs
is 80.

Cases Exposed

Controls Exposed Yes No Total

Yes 12 16 28

No 23 29 52

Total 35 45 80

(a) Compute chi-square for this matched sample case.

(b) Compute the odds ratio and its 95% confidence limit. Write in words what

11.4 In a health survey, adult respondents were asked if they had ever been assaulted
by a domestic partner or spouse. The results were obtained for those who were
currently living with their partner or spouse and for those who were separated
or divorced. There were 262 adults who reported that they were currently living
with their partner or spouse and 28 of these 262 reported having been assaulted.
Of the 105 adults who were currently separated or divorced, 33 reported having
been assaulted. Test if there is an association between having been assaulted
and currently living with your partner or spouse. Compute the odds ratio.

11.5 In a casekontrol study of patients with gallstones, information on coffee con-
sumption was obtained. Among the 80 controls, 35 reported drinking at least 4
cups of coffee per day, whereas 22 of the 82 cases drank 4 or more cups. Test
whether cases and controls drink the same amount of coffee.

11.6 The following table is based on samples of patients diagnosed with gastric
cancer, peptic ulcer, and controls from the same health maintenance operation.
From the following table, test whether there are significant differences in blood
type among the three groups.

this odds ratio means and what this confidence limit implies.

Blood Type Gastric Cancer Peptic Ulcer Controls

0 400 1000 3000

A 400 700 2500

B 75 150 500

AB 25 50 200

Total 900 1900 6200