1. A local farmer is interested in comparing the yields of two varieties of tomatoes. In an experimental field, he selects 20 locations and assigns 10 plants from each variety at random to the locations. He determines the yield per plant (in pounds). The mean yield for plants of variety 1 was = 16.3 pounds with a standard deviation S1 = 3 pounds. The mean yield for plants of variety 2 was =18.4 pounds with a standard deviation S2 = 4 pounds. The standard error of the difference in sample means is
A. 2.10 pounds.
B. 2.50 pounds.
C. 1.58 pounds.
2. A local farmer is interested in comparing the yields of two varieties of tomatoes. In an experimental field, she selects 40 locations and assigns 20 plants from each variety at random to the locations. She determines the average per plant (in pounds). She computes a 95% confidence interval for the difference in mean yields between the two varieties using the two-sample t procedures with the resulting interval (2.13, 6.41). For testing 
using the two-sample t procedures we can say that
A. the P-value could be greater than 0.05.
B. the P-value must be less than 0.05.
C. no information about the P-value can be obtained without the test statistic.
3. A pediatrician is interested in studying the effect of motrin on reducing temperature in young children. Four children with influenza have their temperatures taken immediately before and then 45 minutes after taking a standard dose of motrin with the following results:
A 95% confidence interval for the average reduction in temperature from using motrin is
A. 1.275 ± 1.572.
B. 1.275 ± 1.793.
C. 1.275 ± 1.326.