An environmental group conducted a study to determine whether crows in a certain region were ingesting food containing unhealthy levels of lead. A biologist classified lead levels greater than 4.6 parts per million
(ppm) as unhealthy. The lead levels of a random sample of 23 crows in the region were measured and
recorded. The data are shown in the stemplot.
The mean lead level of the 23 crows in the sample was 4.90 ppm and the standard deviation was 1.12 ppm.
a) Is there convincing evidence (q=0.05) that the mean lead level of crows in this region is
greater than 4.6 parts per million? b) Constructing a 90% confidence interval for this problem yields the values (4.50, 5.30). Does your interval support or contradict your decision from your hypothesis test? Why?