Soal diambil dari buku Berenson, Levine dan Krehbeil Edisi 12
10.68 and 12.79 (PROPORTION 2 SAMPLE)
According to Cencus Estimates, there are about million children between 8 and 12 years old (referred to as TWEENS) in the US in 2009. A recent survey of 1.223 of 8-12 year old children (S. Jayson, “It’s Cooler Than Ever To Be a Tween,” USA Today, February 4, 2009, pp.1A,2A) reported the following results. Suppose the survey was based on 600 boys and 623 girls.
What Tweens Did in the past Week
| Boys | Girls | |
| Played a game on a video game system | 498 | 243 |
| Read a book for fun | 276 | 324 |
| Gave product advice to parents | 186 | 181 |
| Shopped at a mall | 144 | 161 |
For each type of activity, determine whether there is a difference between boys and girls at the 0.01 level of significance.
- Use two sample proportion approach
- Use Chi Square approach
11.12
Integrated ciscuits 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 are as follows:
| New 1 | New 2 | Standard |
| 38 | 29 | 31 |
| 34 | 35 | 23 |
| 38 | 34 | 38 |
| 34 | 20 | 29 |
| 19 | 35 | 32 |
| 28 | 37 | 30 |
Source: Daa extracted from J. Ramirez and W. Taam, “An Autologistic Model for Integrated Circuit Manufacturing, “ Journal of Quality Technology, 2000,32, pp. 254-262.
- At the 0.025 level of significance, is there evidence of a difference in the mean yield among the methods used in the cleansing steps?
- If appropiate, determine which methods differ in mean yields
13.74
Management of soft-drink botting company has the business objective of developing a method for allocating delivery costs to customers. Although one cost clearly relates to travel time required to unload the cases of soft drink at the delivery point. To begin, management decided to develop a regression model to redict delivery time based on the number of cases delivered. A sample of 20 deliveries within a terrirory was selected. The delivery times and the number of cases delivered were organized in the following table.
- Use the least-squares method to compute the regression coefficient bo and b1
- Interpret the meaning of bo and b1 in this problem
- Predict the delivery time for 150 cases of soft drink
9.35
Although many people think they can put a meal on the table in a short period of time, an article reported that they end up spending about 40 minutes doing so. (Data extracted from N. Hellmich, “American Go for the Quick Fix for Dinner,” USA Today, February 14, 2006). Suppose another study conducted to test the validity of this statement. A sample of 25 people is selected, and the length of time to prepare and cook dinner (in minutes) is recorded with the following results:
44.0 51.9 49.7 40.0 55.5 33.0 43.4 41.3 45.2 40.7 41.1 49.1 30.9 45.2 55.3 52.1 55.1 38.8 43.1 39.2 58.6 49.8 43.2 47.9 46.6
Is there evidence that the population mean time to prepare and cook dinner is different from 40 minutes.
10.24
Multiple Myeloma or blood plasma cancer, is characterized by increased blood vessel formulation (angiogenesis) in the bone marrow that is a predictive factor in survival. One treatment approach used for multiple myeloma is stem cell transplantation with the patient’s own stem cells. The following data represent the bone marrow microvessel density for patients who had a complete response to the stem cell transplant (as measured by blood and urine tests). The measurements were taken immadiately prior to the stem cell transplant and at the time the complete response was determined.
At the 0.05 level of significance, is there evidence that the mean bone marrow microvessel density is higher before the stem cell transplant than after the stem cell transplant?
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