E.canis infection is a tick-borne disease of dogs that is sometimes contracted by humans. Among

infected humans, the distribution of white blood cell counts has an unknown mean and a standard

deviation . In the general population, the mean white blood cell count is 8,125/mm3. It is believed that

persons infected with E.canis must on average have lower white blood cell counts.

a. What are the null and alternative hypotheses for a one-sided test?

b. For a sample of 20 infected persons, the mean white blood cell count is = 4,225/mm3 and the

standard deviation is s = 2,780/mm3. Conduct the test at the = 0.05 level.

c. What do you conclude?