The mayor of a large city claims that 30 % of the families in the city earn more than $ 100,000
per year; 52 % earn between $ 30,000 and $ 100,000 (inclusive); 18 % earn less than $ 30,000
In order to test the mayor’s claim, 285 families from the city are surveyed and it is found that:
90 of the families earn more than $ 100,000 per year;
135 of the families earn between $ 30,000 and $ 100,000 per year (inclusive);
60 of the families earn less $ 30,000.
Test the mayor’s claim based on 5 % significance level.
Exam Page 6
A trucking company wants to find out if their drivers are still alert after driving long hours. So,
they give a test for alertness to two groups of drivers. They give the test to 475 drivers who have
just finished driving 4 hours or less and they give the test to 635 drivers who have just finished
driving 8 hours or more. The results of the tests are given below.
Drove 4 hours or less 365 110
Drove 8 hours or more 440 195
Is there is a relationship between hours of driving and alertness? (Do a test for independence.)
Test at the .5 % level of significance.