6.8 Magic mushrooms. A Washington Post article reported that psilocybin, the active ingredient of “magic mushrooms,” promoted a mystical experience in two-thirds of people who took it for the first time, according to a study published in the online journal Psychopharmacology. The authors of the article stated that their “double-blind study evaluated the acute and longer-term psychological effects of a high dose of psilocybin relative to a comparison compound administered under comfortable, supportive conditions.” Explain to someone who knows no statistics what the term “double-blind” means here.

6.9 Do antidepressants help? A researcher studied the effect of an antidepressant on depression. He randomly assigned subjects with moderate levels of depression to two groups. One group received the antidepressant and the other a placebo. Subjects were blinded with respect to the treatment they received. After four weeks, the researcher interviewed all subjects and rated the change in their symptoms based on the comments of subjects during the interview. Critics said that the results were suspect because the ratings were not blind. Explain what this means and how lack of blindness could bias the reported results.

6.10 Treating acne. An article in a medical journal reports an experiment to see if pulsed laser dye therapy is effective in treating acne. The article describes the experiment as a “randomized, controlled, single-blinded, split-face clinical trial of a volunteer sample of 40 patients aged 13 years or older with facial acne conducted at an academic referral center from August 2002 to September 2003.” A split-face clinical trial is one in which one side of the face is treated and one side is not. What do you think “single-blinded” means here? Why isn’t a double-blind experiment possible?

6.11 Bright bike lights. Will requiring bicyclists to use bright, high-intensity xenon lights mounted on the front and rear of the bike reduce accidents with cars by making bikes more visible?

6.12 A high-fat diet prevents obesity? A Science News article reported that according to a study conducted by researchers at Hebrew University of Jerusalem, a high-fat diet could reset the metabolism and prevent obesity. In the study, for 18 weeks, researchers fed a group of mice a high-fat diet on a fixed schedule (eating at the same time and for the same length of time every day). They compared these mice to three control groups: one that ate a low-fat diet on a fixed schedule, one that ate an unscheduled low-fat diet (in the quantity and frequency of its choosing), and one that ate an unscheduled high-fat diet. All four groups of mice gained weight throughout the experiment. However, the mice on the scheduled high-fat diet had a lower final body weight than the mice eating an unscheduled high-fat diet. Surprisingly, the mice on the scheduled high-fat diet also had a lower final body weight than the mice that ate an unscheduled low-fat diet, even though both groups consumed the same amount of calories. In addition, the mice on the scheduled high-fat diet exhibited a unique metabolic state in which the fats they ingested were not stored, but rather utilized for energy at times when no food was available, such as between meals. Briefly discuss the questions that arise in using this experiment to decide the benefits of a scheduled high-fat diet for humans.

6.13 Blood-chilling and strokes. A Science News article reported a study of the effect of cooling the blood of stroke patients on the extent of recovery 90 days after the stroke. Researchers randomly assigned 58 severe-stroke patients to receive either tPA (the standard treatment for stroke) or tPA plus blood-chilling. Regulators overseeing the study required a one-hour delay from the point at which tPA was given before cooling could be started. The researchers found no significant difference in the effects of the two treatments on recovery. Researchers also noted that the recovery rate for both groups was worse than the average seen in stroke patients nationwide but were not concerned. Why were they unconcerned?

6.14 Beating sunburn with broccoli. Some recent studies suggest that compounds in broccoli may be helpful in combating the effects of overexposure to ultraviolet radiation. Based on these studies, we hope to show that a cream consisting of a broccoli extract reduces sunburn pain. Sixty patients suffering from severe sunburn and needing pain relief are available. We will apply the cream to the sunburn of each patient and ask them an hour later, “About what percent of pain relief did you experience?”

6.15 Testing a natural remedy. The statistical controversy presented in this chapter discusses issues surrounding the efficacy of natural remedies. The National Institutes of Health at last began sponsoring proper clinical trials of some natural remedies. In one study at Duke University, 330 patients with mild depression were enrolled in a trial to compare Saint-John’s-wort with a placebo and with Zoloft, a common prescription drug for depression. The Beck Depression Inventory is a common instrument that rates the severity of depression on a 0 to 3 scale.

6.16 The placebo effect. A survey of physicians found that some doctors give a placebo to a patient who complains of pain for which the physician can find no cause. If the patient’s pain improves, these doctors conclude that it had no physical basis. The medical school researchers who conducted the survey claimed that these doctors do not understand the placebo effect. Why?

6.17 The best painkiller for children. A Washington Post article reported a study comparing the effectiveness of three common painkillers for children. Three hundred children, aged 6 to 17, were randomly assigned to three groups. Group A received a standard dose of ibuprofen. Group B received a standard dose of acetaminophen. Group C received a standard dose of codeine. The youngsters rated their pain on a 100-point scale before and after taking the medicine.

6.18 Flu shots. A New York Times article reported a study that investigated whether giving flu shots to schoolchildren protects a whole community from the disease. Researchers in Canada recruited 49 remote Hutterite farming colonies in western Canada for the study. In 25 of the colonies, all children aged 3 to 15 received flu shots in late 2008; in the 24 other colonies, they received a placebo. Which colonies received flu shots and which received the placebo was determined by randomization, and the colonies did not know whether they received the flu shots or the placebo. The researchers recorded the percentage of all children and adults in each colony who had laboratory-confirmed flu over the ensuing winter and spring.

6.19 Ibuprofen and atherosclerosis. The theory of atherosclerosis (hardening and narrowing of the arteries) emphasizes the role of inflammation in the vascular walls. Because ibuprofen is known to possess a wide range of anti-inflammatory actions, it was hypothesized that it might help in the prevention of atherosclerotic lesion development. Both a low-cholesterol and a high-cholesterol diet were used, as the extent of atherosclerosis is also affected by diet. Thirty-two New Zealand rabbits served as subjects in the experiment and, after three months, the percentage of the surface covered by atherosclerotic plaques in a region of the aorta was evaluated. Although ibuprofen did suppress the expression of a gene thought to be related to atherosclerosis, it was not shown to have an effect on the extent of fat-induced atherosclerotic lesions.

6.20 Price change and fairness. A marketing researcher wishes to study what factors affect the perceived fairness of a change in the price of an item from its advertised price. In particular, does the type of change in price (an increase or decrease) and the source of the information about the change affect the perceived fairness? In an experiment, 20 subjects interested in purchasing a new rug are recruited. They are told that the price of a rug in a certain store was advertised at $500. Subjects are sent, one at a time, to the store, where they learn that the price has changed. Five subjects are told by a store clerk that the price has increased to $550. Five subjects learn that the price has increased to $550 from the price tag on the rug. Five subjects are told by a store clerk that the price has decreased to $450. Five subjects learn that the price has decreased to $450 from the price tag on the rug. After learning about the change in price, each subject is asked to rate the fairness of the change on a 10-point scale with 1 = “very unfair” to 10 = “very fair.”

6.21 Liquid water enhancers. Bottled water, flavored and plain, is expected to become the largest segment of the liquid refreshment market by the end of the decade, surpassing traditional carbonated soft drinks. Kraft’s MiO, a liquid water enhancer, comes in a variety of flavors, and a few drops added to water gives a zero-calorie, flavored water drink. You wonder if those who drink flavored water like the taste of MiO as well as they like the taste of a competing flavored water product that comes ready to drink. Describe a matched pairs design to answer this question. Be sure to include any blinding of your subjects. What is your response variable going to be?

6.22 Athletes take oxygen. We often see players on the sidelines of a football game inhaling oxygen. Their coaches think this will speed their recovery. We might measure recovery from intense exertion as follows: Have a football player run 100 yards three times in quick succession. Then allow three minutes to rest before running 100 yards again. Time the final run. Describe the design of two experiments to investigate the effect of inhaling oxygen during the rest period. One of the experiments is to be a completely randomized design and the other a matched pairs design in which each student serves as his or her own control. Twenty football players are available as subjects. In both experiments, carry out the randomization required by the design.

6.23 Font naturalness and perceived healthiness. Can the font used in a packaged product affect our perception of the product’s healthiness? It was hypothesized that use of a natural font, which looks more handwritten and tends to be more slanted and curved, would lead to a higher perception of product healthiness than an unnatural font. Two fonts, Impact and Sketchflow Print, were used. These fonts were shown in a previous study to differ in their perceived naturalness, but otherwise were rated similarly on factors such as readability and likeability. Images of two identical packages, differing only in the font used, were available to be presented to the subjects. Participants read statements such as, “This product is healthy,” “This product is wholesome,” This product is natural,” and “This product is organic.” They then rated how much they agreed with the statements on a seven-point scale with “1” indicating strong agreement and “7” indicating strong disagreement. Each subject’s responses were combined to create a perceived healthiness score. The researchers have 100 students available to serve as subjects.

6.24 Technology for teaching statistics. The Brigham Young University statistics department performed randomized comparative experiments to compare teaching methods. Response variables include students’ final-exam scores and a measure of their attitude toward statistics. One study compared two levels of technology for large lectures: standard (overhead projectors and chalk) and multimedia. The individuals in the study were the eight lectures in a basic statistics course. There were four instructors, each of whom taught two lectures. Because lecturers differed, a block design was used with their lectures forming four blocks. Suppose the lectures and lecturers were as follows.

Use a diagram to outline a block design for this experiment. Figure 6.2 is a model.

6.25 Comparing weight-loss treatments. Twenty overweight females have agreed to participate in a study of the effectiveness of four weight-loss treatments: A, B, C, and D. The researcher first calculates how overweight each subject is by comparing the subject’s actual weight with her “ideal” weight. The subjects and their excess weights in pounds are

The response variable is the weight lost after eight weeks of treatment. Because a subject’s excess weight will influence the response, a block design is appropriate.

6.26 In the corn field. An agronomist (a specialist in crop production and soil chemistry) wants to compare the yield of four corn varieties. The field in which the experiment will be carried out increases in fertility from north to south. The agronomist therefore divides the field into 20 plots of equal size, arranged in five east-west rows of four plots each, and employs a block design with the rows of plots as the blocks.

6.27 Better sleep? Is the time between when you go to bed and when you first wake up affected by the time you eat dinner and how much exercise you do during the day? Describe briefly the design of an experiment with two explanatory variables to investigate this question. Be sure to specify the treatments exactly and to tell how you will handle lurking variables such as amount of sleep the previous night.

6.28 Dunkin’ Donuts versus Starbucks. Do consumers prefer the taste of a latte from Dunkin’ Donuts or from Starbucks in a blind test in which neither latte is identified? Describe briefly the design of a matched pairs experiment to investigate this question.

6.29 What do you want to know? The previous two exercises illustrate the use of statistically designed experiments to answer questions that arise in everyday life. Select a question of interest to you that an experiment might answer and briefly discuss the design of an appropriate experiment.

6.30 Doctors and nurses. Nurse practitioners are nurses with advanced qualifications who often act much like primary-care physicians. An experiment assigned 1316 patients who had no regular source of medical care to either a doctor (510 patients) or a nurse practitioner (806 patients). All the patients had been diagnosed with asthma, diabetes, or high blood pressure before being assigned. The response variables included measures of the patients’ health and of their satisfaction with their medical care after six months.