1. Some researchers have conjectured that stem-pitting disease in peach-tree seedlings might be controlled through weed and soil treatment. An experiment was conducted to compare peach-tree seedling growth with soil and weeds treated with one of two herbicides.
In a field containing ten seedlings, five were randomly selected throughout the field and assigned to receive Herbicide A. The remainder received Herbicide B. Soil and weeds for each seedling were treated with the appropriate herbicide, and at the end of the study period the height in (cm) was recorded for each seedling. The following results were obtained:
A 90% confidence interval for the difference in mean heights for the two herbicides is (0.2, 14.6). Which statement is correct?
A. The P-value for a test of the null hypothesis of equal means and the alternative of different means would be greater than 10% since the interval doesn't include 0.
B. A 95% confidence could not include zero either, since we would be even more confident of a difference in the groups.
C. Neither is correct.
2. I did an eggsperiment with a fellow instructor one day. His calculus class was studying volumes of solids by rotating curves around the x-axis. We modeled the volume of an egg as an ellipsoid, and measured eggs with calipers, using the calculus formula. Each egg was also measured for volume using a water displacement method. We wanted to know if the two methods agreed or not. The data were
The value of the test statistic for the test is
A. t = 0.975.
B. t = 0.387.
C. z = 0.975.