Chapter 4 MCQ Practice

A researcher for a consumer products company is field testing a new formula for laundry detergent. He has contracted with 60 families, each with two children, who have agreed to test the product. He randomly assigns 30 families to the group that will use the new formula and 30 to the group that will use the company's current detergent formula. The most important reason for this random assignment is that

1. randomization is a good way to create two groups of 30 families that are as similar as possible, so that comparisons can be made between the two groups.

2. randomization eliminates the impact of any confounding variables.

3. randomization reduces the impact of outliers.

4. randomization ensures that the study is double-blind.

5. randomization makes the analysis easier since the data can be collected and entered into the computer in any order.

1. randomization is a good way to create two groups of 30 families that are as similar as possible, so that comparisons can be made between the two groups.

A maple manufacturer wants to estimate the average trunk diameter of Sugar Maples trees in a large forest. There are too many trees to list them all and take a SRS, so he divides the forest into several hundred 10 meter by 10 meter plots, selects 25 plots at random, and measures the diameter of every Sugar Maple in each one. This is an example of a 

1. stratifed sample

2. cluster sample

3. convenience sample

4. simple random sample

5. multi-stage sample

2. cluster sample

There are ten departments at SMART University. To conduct a survey, a researcher selects ten faculty members randomly from each department. The sample selected in this way is called a:

1. simple random sample

2. voluntary response sample

3. stratifed random sample

4. multi-stage response sample

5. systematic sample

3. stratified random sample

A nutritionist wants to study the effect of storage time (6, 12, and 18 months) on the amount of vitamin C present in freeze dried fruit when stored for these lengths of time. Six fruit packs were randomly assigned to each of the three storage times. The treatment, experimental unit, and response are respectively:

1. A specific storage time, a fruit pack, amount of vitamin C

2. A fruit pack, amount of vitamin C, a specific storage time

3. A specific storage time, amount of vitamin C, a fruit pack

4. A specific storage time, six fruit packs, amount of vitamin C

5. Random assignment, a fruit pack, amount of vitamin C

1. A specific storage time, a fruit pack, amount of vitamin C

A new headache remedy was given to a group of 25 subjects who had headaches. Four hours after taking the new remedy, 20 of the subjects reported that their headaches had disappeared. From this information you conclude:

1. that the remedy is not effective for the treatment of headaches.

2. nothing because there is no control group for comparison.

3. that the new treatment is better than aspirin.

4. nothing, because the sample size is too small.

5. that the remedy is effective for the treatment of headaches.

2. nothing because there is no control group for comparison.

The following numbers appear in a table of random digits:

38683 50279 38224 09844 13578 28251 12708 24684

A scientist will be measuring the total amount of leaf litter in a random sample (n = 5) of forest sites selected without replacement from a population of 45 sites. The sites are labeled 01, 02, ..., 45 and she starts at the beginning of the line of random digits and takes consecutive pairs of digits. Which of the following is correct?

1. Her sample is 38, 25, 02, 38, 22

2. Her sample is 38, 35, 02, 22, 40

3. Her sample is 38, 35, 27, 28, 08

4. Her sample is 38, 65, 35, 02, 79

5. Her sample is 38, 68, 35, 02, 22

2. Her sample is 38, 35, 02, 22, 40

A researcher observes that, on average, the number of divorces in cities with Major League Baseball teams is larger than in cities without Major League Baseball teams. Which of the following is the most plausible explanation for this observed association?

1. The high number of divorces is responsible for the presence of Major League Baseball teams (more single men means potentially more fans at the ballpark, making it attractive for an owner to relocate to such cities).

2. The association is die to a lurking variable (Major League teams tend to be in large cities with more people, hence a greater number of divorces).

3. The presence of a Major League Baseball team causes the number of divorces to rise (perhaps husbands are spending too much time at the ballpark).

4. The association is purely coincidental. It is implausible to believe the observed association could be anything other than accidental.

5. The association makes no sense, since many married couples go to the ballpark together.

2. The association is die to a lurking variable (Major League teams tend to be in large cities with more people, hence a greater number of divorces).

A survey was done in the town of Mechanicsville to estimate the proportion of cars that are red and made by companies based in Japan. A simple random sample of 25 cars from a parking lot at Lee Davis High School was taken. Which of the following statements is correct?

1. If a simple random sample of 15 cars were taken, we would expect the same amount of variability in the proportion of red cars as we would with a sample of 25 cars.

2. Since this is a simple random sample, it should be representative of all cars in Mechanicsville.

3. The results would be the same regardless of the time of day that the sample is taken.

4. A different team doing the sampling independently would probably obtain a slightly different answer for their sample proportion.

5. An alternative method for getting a representative sample would be to select the 25 cars closest to a specified location, such as the entrance to the gymnasium.

4. A different team doing the sampling independently would probably obtain a slightly different answer for their sample proportion.