Introductory Biostatistics

Of the 180 left-handed students, 93 reported at least one injury. In the

same period, 619 of the 1716 right-handed students reported at least one

injury. Test to compare the proportions of injured students, left-handed

versus right-handed; state clearly your null and alternative hypotheses

and choice of test size.

6.9 In a study conducted to evaluate the hypothesis that tea consumption

and premenstrual syndrome are associated, 188 nursing students and 64

tea factory workers were given questionnaires. The prevalence of pre-

menstrual syndrome was 39% among the nursing students and 77%

among the tea factory workers. Test to compare the prevalences of pre-

menstrual syndrome, tea factory workers versus nursing students; state

clearly your null and alternative hypotheses and choice of test size.

6.10 A study was conducted to investigate drinking problems among college
students. In 1983, a group of students were asked whether they had ever
driven an automobile while drinking. In 1987, after the legal drinking
age was raised, a di¤erent group of college students were asked the same
question. The results are as shown in Table E6.10. Test to compare the
proportions of students with a drinking problem, 1987 versus 1983; state
clearly your null and alternative hypotheses and choice of test size.

TABLE E6.10

Year

Drove While

Drinking 1983 1987

Yes 1250 991

No 1387 1666

Total 2637 2657

6.11 In August 1976, tuberculosis was diagnosed in a high school student
(index case) in Corinth, Mississippi. Subsequently, laboratory studies
revealed that the student’s disease was caused by drug-resistant tubercule
bacilli. An epidemiologic investigation was conducted at the high school.
Table E6.11 gives the rates of positive tuberculin reaction determined for
various groups of students according to the degree of exposure to the
index case. Test to compare the proportions of students with infection,
high exposure versus low exposure; state clearly your null and alternative
hypotheses and choice of test size.

TABLE E6.11

Exposure Level Number Tested Number Positive

High 129 63

Low 325 36

EXERCISES 237