Exam 12: Experimental Design: Controlling Variation

Suppose a new engine additive is designed to improve performance in race cars and researchers wish to test the effectiveness of the new additive. On a closed race course, the individual race times for forty race cars are recorded. The race times (on the same course)for each of the cars after being treated with the engine additive are then recorded. Which test design would be most appropriate for this scenario?

Use the following information to answer the question. 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. -Choose the statement that restates the conclusion of the study in terms of cause- and- effect conclusion.

A newspaper reporter is interested in the outcome of a local election on a controversial issue. She knows that opinions of voters who visit the polls in the morning could be different than those who visit later in the day and she does not want a biased sample. Which sampling method is likely to result in an unbiased sample?

Use the following information to answer the question. Which treatment is most effective at treating bathroom mildew: water mixed with vinegar, ammonia, or soap? In a study, researchers randomly assigned 55 similar tile samples with similar amounts of mildew to one of three groups. Depending on which group they were assigned to, each tile sample received a home remedy of water mixed with vinegar, ammonia, or soap. Afterwards, each tile sample was examined and any remaining mildew was measured. Researchers found that a soap and water mixture produced better results than both vinegar and ammonia. -Is this a controlled experiment or an observational study? Explain.

A chocolate chip manufacturer has developed a new recipe for its chocolate chips and is planning a consumer taste test. Researchers in the test kitchen want to measure whether there is a difference in consumer opinions between the old recipe and the new recipe. Company researchers believe that consumer reaction to the new chip will depend on age so they decide to block on age. To do this, they create blocks for consumers between the ages 12- 18 years, 19- 25 years, 26- 32 years, and 32 years and older. They then randomly assign subjects in each block to taste cookies made with the new and old recipe chocolate chip. Following the taste test, participants respond to a questionnaire about the cookies they tasted. Is this an effective design for this study?

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

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

Suppose a manufacturer of rearview mirrors decides to inspect every fifteenth part for defects. What kind of sampling does this illustrate?

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

Suppose the CEO of a large corporation is interested in finding out whether a newly instituted program about professionalism in the workplace is effective. A statistician divides the employees into three job types then randomly selects a sample of employees from each job type. Participants are then asked to fill out a questionnaire about professionalism in the workplace. What kind of sampling does this illustrate?

Which energy drink is better? In a study, researchers randomly assigned 50 similar adults to one of three groups. All subjects were allowed to sleep for eight hours followed by staying awake for ten hours. Depending on which group they were assigned to, subjects then drank 12 ounces of strong coffee, a name brand "5- hour" energy drink, or 16 oz of a name brand sports drink containing caffeine and vitamins. Afterwards, subjects were measured for mental fatigue. Researchers found that the adults that drank strong coffee after being awake for ten hours were less fatigued than either those who drank the "5- hour" energy drink or the sports drink. For this controlled experiment, identify the treatment and the response variables.

Write at least two questions that you should ask yourself when reading articles containing statistical research results. Explain why these questions are important.

Use the following information to answer the question. A researcher wonders whether speed of service at a diner is affected by whether a male customer is wearing a suit jacket. The researcher used the following study design to collect data: The researcher chose five diners in a large city and recorded the number of male customers that wore a suit jacket during a two week period. He also records how long it took a waiter or waitress to address the customer. He finds that male customers who wear suit jackets were addressed by the wait staff faster than male customers who did not wear a suit jacket. -Choose the statement that correctly explains why we can or cannot generalize these results to a larger population.

Use the following information to answer the question. These two headlines are on the same topic. Headline A: Married men who gain weight following the birth of their first child dramatically increase their risk of further weight gain following the birth of more children, a new study suggests. Headline B: Married male weight gain after the birth of the first child leads to additional weight gain following the birth of more children, a new study finds. -Which one has language that suggests a cause- and- effect relationship?

Use the following information to answer the question. Which treatment is most effective at treating head lice: Benzyl alcohol lotion, dandruff shampoo, or mayonnaise? In a study, researchers randomly assigned 55 subjects with head lice to one of three groups. All subjects had similar cases of head lice. Depending on which group they were assigned to, subjects received an over- the- counter remedy of Benzyl alcohol lotion, dandruff shampoo, or mayonnaise, which was applied by a trained professional. Afterwards, each subject was examined and any lice or eggs found were counted. Researchers found that Benzyl alcohol lotion produced better results than both dandruff shampoo and mayonnaise. -Choose the statement that restates the conclusion of the study in terms of cause- and- effect conclusion.

Use the following information to answer the question. 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?

Use the following information to answer the question. Which treatment is most effective at treating head lice: Benzyl alcohol lotion, dandruff shampoo, or mayonnaise? In a study, researchers randomly assigned 55 subjects with head lice to one of three groups. All subjects had similar cases of head lice. Depending on which group they were assigned to, subjects received an over- the- counter remedy of Benzyl alcohol lotion, dandruff shampoo, or mayonnaise, which was applied by a trained professional. Afterwards, each subject was examined and any lice or eggs found were counted. Researchers found that Benzyl alcohol lotion produced better results than both dandruff shampoo and mayonnaise. -Was this an observational study or a controlled experiment?

Suppose state lawmakers are interested in finding out whether a newly instituted elementary school program about bullying is effective. A statistician divides the state into three regions then randomly selects a sample of thirty elementary schools from each region. Students at the selected schools complete a questionnaire about bullying. What kind of sampling does this illustrate?

Describe one benefit to a stratified sampling plan.