Question: A nurse was hired by a governmental ecology agency to investigate the impact of a lead smelter on the level of lead in the blood of children living near the smelter. Ten children were chosen at random from those living near the smelter. A comparison group of seven children was randomly selected from those living in an area relatively free from possible lead pollution. Blood samples were taken from the children and lead levels determined. The following are the results (scores are in micrograms of lead per 100 milliliters of blood.

Lead Levels

Children living near smelter Children living in unpolluted area

18 9

16 13

21 8

14 15

17 17

19 12

22 11

24

15

18

a. What is the alternative hypothesis? Assume that a nondirectional hypothesis is warranted.

b. What is the null hypothesis?

c. What is the value of t obtained.

d. What is the value of t-critical.

d. What might the candidate conclude using α = 0.05 _{2 tail}?

e. What type error might the candidate have made?

f. Estimate the size of the real effect using omega squared and cohen’s d. Is the effect a large one?