1. Students in a business course performed a completely randomized design to test the strength of four brands of trash bags. One-pound weights were placed into a bag, one at a time, until the bag broke. A total of 40 bags, 10 for each brand, were used.
a. at the .05 level of significance, is there evidence of a difference in the mean strength of the four brands of trash bags?
b. if appropriate, determine which brands differ in mean strength
c. at the .05 level of significance, is there evidence of a difference in the variation in strength among the four brands of trash bags?
d. Which brands should you buy, and which brands should you avoid? Explain.
2. Integrated circuits are manufactured on silicon wafers through a process that involves a series of steps. An experiment was carried out to study the effect on the yield of using three methods in the cleansing step (coded to maintain confidentiality). The results (stored in Yield-One Way) are as follows:
| New1 |
New2 |
Standard |
| 38 |
29 |
31 |
| 34 |
35 |
23 |
| 38 |
34 |
38 |
| 34 |
20 |
29 |
| 19 |
35 |
32 |
| 28 |
37 |
30 |
a. At the 0.05 level of significance, is there evidence of a difference in the mean yield among the methods used in the cleansing steps?
b. If appropriate, determine which methods differ in mean yields.
c. At the 0.05 level of significance, is there evidence of a difference in the variation in yields among the different methods?
d. What effect does your result in (c) have on the validity of the results in (a) and (b)?
Data
| KROGER |
GLAD |
HEFTY |
TUFFSTUFF |
| 34 |
32 |
33 |
26 |
| 30 |
42 |
34 |
18 |
| 40 |
34 |
32 |
20 |
| 38 |
36 |
40 |
15 |
| 36 |
32 |
40 |
20 |
| 30 |
40 |
34 |
20 |
| 30 |
36 |
36 |
17 |
| 42 |
43 |
34 |
18 |
| 36 |
30 |
32 |
19 |
| 38 |
38 |
34 |
20 |