An experiment to compare the tension bond strength of polymer latex modified mortar (Portland cement mortar to which polymer latex emulsions have been added during mixing) to that of unmodified mortar resulted in x = 18.19 kgf/cm2 for the modified mortar (m = 42) and y = 16.87 kgf/cm2 for the unmodified mortar (n = 32). Let m1 and m2 be the true average tension bond strengths for the modified and unmodified mortars, respectively. Assume that the bond strength distributions are both normal.
(a) Assuming that ?1 = 1.6 and ?2 = 1.3, testH0: m1 ? m2 = 0versus Ha: m1 ? m2 > 0 at level 0.01.State the rejection region(s). (If the critical region is one-sided, enter NONE for the unused region. Round your answers to two decimal places.)
z ?
z ?
Compute the test statistic value. (Round your answer to two decimal places.)
z =
State the conclusion in the problem context.
Reject H0. The data does not suggest that the difference in average tension bond strengths exceeds 0.
Fail to reject H0. The data does not suggest that the difference in average tension bond strengths exceeds from 0.
Fail to reject H0. The data suggests that the difference in average tension bond strengths exceeds 0.
Reject H0. The data suggests that the difference in average tension bond strengths exceeds 0.
(b) Compute the probability of a type II error for the test of part (a) when m1 ? m2 = 1.(Round your answer to four decimal places.)
(c) Suppose the investigator decided to use a level 0.05 test and wished ? = 0.10 when m1 ? m2 = 1. If m = 42, what value of n is necessary? (Round your answer up to the nearest whole number.)
n =
(d) How would the analysis and conclusion of part (a) change if ?1 and ?2 were unknown but s1 = 1.6 and s2 = 1.3?
Since n = 32 is not a large sample, it would no longer be appropriate to use the large sample test. A small sample t procedure should be used, and the appropriate conclusion would follow.
Since n = 32 is a large sample, it would be more appropriate to use the t procedure. The appropriate conclusion would follow. Since n = 32 is a large sample, it would no longer be appropriate to use the large sample test. Any other test can be used, and the conclusions would stay the same.
Since n = 32 is not a large sample, it still be appropriate to use the large sample test. The analysis and conclusions would stay the same.