Question

Researchers interested in lead exposure due to car exhaust sampled the blood of 52 randomly selected
police officers who were (as part of their job) subjected to constant inhalation of gas fumes while working
traffic enforcement. All chosen police officers worked in urban areas. The mean blood lead concentration
was 124.32 units, with a standard deviation of 37.74 units. A previous study of police officers who worked
in a suburb found a mean blood lead concentration of 35 units.
(a) Compute the effect size. Is this basically no effect, a small effect, a moderate effect, or a strong effect?
(b) Does this data provide convincing evidence that police officers in the urban area appear to have a
higher concentration of lead in their blood than officers in the suburb? Note: The term “convincing
evidence” is a key word that tells you to conduct a hypothesis test. Be sure to show all 6 steps,
interpret your p-value, and give your conclusion in the context of the data. Use α = 0.01.
(c) What does this choice of α mean in words?
(d) Based on the result of your hypothesis test, would you expect a 98% confidence interval for mean
blood concentration to contain 35 units? Explain.

Answer 1