Exam 12: Experimental Design: Controlling Variation

Which statement is not true about randomized block designs?

Use the following information for following questions:. These two headlines are on the same topic. Headline A: Children who view advertisements for fast food dramatically increase their risk of becoming obese adolescents, a new study suggests. Headline B: Viewing advertisements for fast food leads to childhood obesity, a new study finds. -Was the study referenced most likely a controlled experiment or an observational study? Explain.

Which of the following is not an important principle that should always be kept in mind when reading research articles containing statistical research results?

A small study was conducted on a new procedure for treating atrial fibrillation. The study involved a new way to perform ablation surgery. One method currently being used had a success rate of only 50% in preventing additional episodes of atrial fibrillation within one year. The new method of performing ablation surgery was performed on 8 patients and 6 of the 8 patients did not suffer additional episodes of atrial fibrillation within one year. Choose the statement that best summarizes the significance of this result.

Use the following information for following questions:. Often college students taking an introductory course in psychology are required to participate in research experiments. One experiment was performed to see if using colored paper increased reading comprehension. One hundred students enrolled in an introductory college psychology course volunteered to participate in the study. Fifty of the students were randomly chosen to read a chapter in a psychology test that was printed on yellow paper and the remaining fifty students were given the same chapter to read printed on white paper. After reading the chapter, each student was asked to answer a series of questions to test his/her comprehension. The results indicated that those students reading the chapter printed on yellow paper tended to have higher comprehension scores than those students reading the chapter printed on white paper. -Choose the statement that correctly explains why we can or cannot make a cause-and-effect conclusion.

A publisher is considering publishing a new magazine about environmentally-friendly living in the city and plans to gage interest in the magazine using potential consumers. Company researchers want to measure whether there is a difference in opinion between the new magazine and the competing publication. Company researchers believe that consumer reaction to the new magazine will depend on age so they decide to block on age. To do this, they create blocks for consumers between the ages 18-24 years, 25-32 years, 33-45 years, and 46 years and older. They then randomly select two of the blocks to read the first issue of the new magazine and the other two blocks to read a similar competing publication. Following the test, participants respond to a questionnaire about the magazine they read. Is this an effective design for the study? If not, describe an improvement.

Suppose a sociologist is interested in finding out if there is an association between gender and opinions on human cloning. Which test design would be most appropriate for this scenario?

Which of the following is not a benefit of a stratified sampling plan?

Use the following information to answer questions (5) - (7). A tire manufacturer has made some modifications to its most popular tire and wants to see if the tread on the modified tire will last longer than the original tire. Because there is much variation in the way people drive, the manufacturer decides to use blocking to reduce this variation. Twenty cars will be used to test the tires. Ten cars are randomly selected to receive an original tire on the right rear wheel and a modified tire on the left rear wheel. The remaining ten cars will receive an original tire on the left rear wheel and a modified tire on the right rear wheel. Each car will then be driven 10,000 miles and the amount of wear recorded for each wheel. -Which test design would be most appropriate for this scenario?

Use the following information to answer questions (1) - (3). Scientists were interested in determining if the amount of nicotine present in tobacco leaves is related to the amount of water received by the plants. In a greenhouse, a total of 120 tobacco plants were selected. During the growing season, 30 plants were randomly assigned to receive the normal amount of water, 30 plants received 75% of the normal amount of water, 30 plants received 50% of the normal amount of water, and 30 plants received 25% of the normal amount of water. At the end of the growing season, one leaf was selected at random from each plant and the amount of nicotine present was recorded for each. Researchers determined that leaves from tobacco plants receiving the normal amount of water during the growing season had more nicotine than leaves from tobacco plants receiving less water. -Was this an observational study or a controlled experiment?

Use the following information to answer questions (5) - (7). A tire manufacturer has made some modifications to its most popular tire and wants to see if the tread on the modified tire will last longer than the original tire. Because there is much variation in the way people drive, the manufacturer decides to use blocking to reduce this variation. Twenty cars will be used to test the tires. Ten cars are randomly selected to receive an original tire on the right rear wheel and a modified tire on the left rear wheel. The remaining ten cars will receive an original tire on the left rear wheel and a modified tire on the right rear wheel. Each car will then be driven 10,000 miles and the amount of wear recorded for each wheel. -Is this a correct use of blocking?

Suppose a gumball manufacturer decides to inspect every twenty-fifth gumball for defects. What kind of sampling does this illustrate?

Which of the following is not a primary factor that affects the power of a test?

Use the following information for following questions:. Which treatment is most effective at treating carpet stains: vinegar, ammonia, or hydrogen peroxide? In a study, researchers randomly assigned 55 carpet samples with identical stains to one of three groups. Depending on which group they were assigned to, each carpet sample received a home remedy of water mixed with vinegar, ammonia, or hydrogen peroxide. Afterwards, each carpet sample was examined and any remaining stain was measured. Researchers found that a vinegar and water mixture produced better results than both ammonia and hydrogen peroxide. -Was this a controlled experiment or an observational study?

The city council of a moderate size city wants to gather input from the citizens of the city on the proposed expansion to the local airport. It has been decided that a stratified sampling plan would be the best way to get the desired information because opinions within the strata are likely to be similar. Which method of stratifying seems to be the most reasonable for this situation?

Which of the following statements is not true about a systematic sampling plan?

A coin collector has over 54 books containing varying number of coins of various denominations. He is very interested in knowing the value of the collection, but does not want to take the time to look up the value of each coin in the collection. He decides to randomly select 4 books and determines the value of each coin in each of the 4 books by looking up the coin in an online pricing book. What kind of sampling does this illustrate?

Suppose the president of a large company is in the process of deciding whether to adopt a lunchtime exercise program.The purpose of the program is to improve the health of the employees and thus, reduce the medical expenses. To get more information, he instituted the exercise program for all the employees in one office. The president knows that during the winter months medical expenses are relatively high because of high occurrences of colds and flu. Therefore, he records the medical expenses of the employees in the

Use the following information for following questions:. These two headlines are on the same topic. Headline A: Children who view advertisements for fast food dramatically increase their risk of becoming obese adolescents, a new study suggests. Headline B: Viewing advertisements for fast food leads to childhood obesity, a new study finds. -Which one has language that suggests a cause- and effect relationship? Is this problematic? Can you think of a confounding factor other than exposure to fast food advertisements that might cause childhood obesity?

A study is to be undertaken to determine the teacher workload in the public schools in a large county in California. The target population is all high school teachers (grades 9 - 12) with at least one year of experience. The county contains a total of thirty-seven public high schools and a total of 4,857 teachers. All teachers selected in the sample will be asked to complete a short survey. Describe a sampling plan that would allow the researchers to obtain the desired information.