1. Intro to Stats and Collecting Data

Insomnia Researchers wanted to test the effectiveness of a new cognitive behavioral therapy (CBT) compared with both an older behavioral treatment and a placebo therapy for treating insomnia. They identified 75 adults with insomnia. Patients were randomly assigned to one of three treatment groups. Twenty-five patients were randomly assigned to receive CBT (sleep education, stimulus control, and time-in-bed restrictions), another 25 received muscle relaxation training (RT), and the final 25 received a placebo treatment. Treatment lasted 6 weeks, with follow-up conducted at 6 months. To measure the effectiveness of the treatment, researchers used wake time after sleep onset (WASO). CBT produced larger improvements than did RT or placebo treatment. For example, the CBT-treated patients achieved an average 54% reduction in their WASO, whereas RT-treated and placebo-treated patients, respectively, achieved only 16% and 12% reductions in this measure. Results suggest that CBT treatment leads to significant sleep improvements within 6 weeks, and these improvements appear to endure through 6 months of follow-up. 53 Source: Jack D. Edinger, PhD; William K. Wohlgemuth, PhD; Rodney A. Radtke, MD; Gail R. Marsh, PhD; Ruth E. Quillian, PhD. “Cognitive Behavioral Therapy for Treatment of Chronic Primary Insomnia,” Journal of the American Medical Association 285: 1856–1864, 2001

What is the population being studied?

Insomnia Researchers wanted to test the effectiveness of a new cognitive behavioral therapy (CBT) compared with both an older behavioral treatment and a placebo therapy for treating insomnia. They identified 75 adults with insomnia. Patients were randomly assigned to one of three treatment groups. Twenty-five patients were randomly assigned to receive CBT (sleep education, stimulus control, and time-in-bed restrictions), another 25 received muscle relaxation training (RT), and the final 25 received a placebo treatment. Treatment lasted 6 weeks, with follow-up conducted at 6 months. To measure the effectiveness of the treatment, researchers used wake time after sleep onset (WASO). CBT produced larger improvements than did RT or placebo treatment. For example, the CBT-treated patients achieved an average 54% reduction in their WASO, whereas RT-treated and placebo-treated patients, respectively, achieved only 16% and 12% reductions in this measure. Results suggest that CBT treatment leads to significant sleep improvements within 6 weeks, and these improvements appear to endure through 6 months of follow-up. 53 Source: Jack D. Edinger, PhD; William K. Wohlgemuth, PhD; Rodney A. Radtke, MD; Gail R. Marsh, PhD; Ruth E. Quillian, PhD. “Cognitive Behavioral Therapy for Treatment of Chronic Primary Insomnia,” Journal of the American Medical Association 285: 1856–1864, 2001

What is the response variable in this study?

The Memory Drug? Researchers wanted to evaluate whether ginkgo, an over-the-counter herb marketed as enhancing memory, improves memory in elderly adults as measured by objective tests. To do this, they recruited 98 men and 132 women older than 60 years and in good health. Participants were randomly assigned to receive ginkgo, 40 milligrams (mg) 3 times per day, or a matching placebo. The measure of memory improvement was determined by a standardized test of learning and memory. After 6 weeks of treatment, the data indicated that ginkgo did not increase performance on standard tests of learning, memory, attention, and concentration. These data suggest that, when taken following the manufacturer’s instructions, ginkgo provides no measurable increase in memory or related cognitive function to adults with healthy cognitive function.

What is the factor that is set to predetermined levels? What are the treatments?

Platelet-Rich Plasma Does a platelet-rich plasma (PRP) injection into the scalp promote hair growth? Researchers identified 30 female patients with female pattern hair loss. The patients ranged in age from 20 to 45 years. For each patient, two areas with hair loss were identified. A coin toss was used to decide which area received the PRP injection and which received a saline injection. Injections were given to each patient at one-week intervals. After 6 months the change in the patients’ hair density (number of hairs per square centimeter) and hair diameter (millimeters) was measured. The mean difference in hair density (PCP minus saline) was 59.47 hairs/cm2 and the mean difference in hair thickness was 0.08 mm.

What type of experimental design is this?

Platelet-Rich Plasma Does a platelet-rich plasma (PRP) injection into the scalp promote hair growth? Researchers identified 30 female patients with female pattern hair loss. The patients ranged in age from 20 to 45 years. For each patient, two areas with hair loss were identified. A coin toss was used to decide which area received the PRP injection and which received a saline injection. Injections were given to each patient at one-week intervals. After 6 months the change in the patients’ hair density (number of hairs per square centimeter) and hair diameter (millimeters) was measured. The mean difference in hair density (PCP minus saline) was 59.47 hairs/cm2 and the mean difference in hair thickness was 0.08 mm.

What is the population that is being studied?

Platelet-Rich Plasma Does a platelet-rich plasma (PRP) injection into the scalp promote hair growth? Researchers identified 30 female patients with female pattern hair loss. The patients ranged in age from 20 to 45 years. For each patient, two areas with hair loss were identified. A coin toss was used to decide which area received the PRP injection and which received a saline injection. Injections were given to each patient at one-week intervals. After 6 months the change in the patients’ hair density (number of hairs per square centimeter) and hair diameter (millimeters) was measured. The mean difference in hair density (PCP minus saline) was 59.47 hairs/cm2 and the mean difference in hair thickness was 0.08 mm.

What are the response variables in this study?

Platelet-Rich Plasma Does a platelet-rich plasma (PRP) injection into the scalp promote hair growth? Researchers identified 30 female patients with female pattern hair loss. The patients ranged in age from 20 to 45 years. For each patient, two areas with hair loss were identified. A coin toss was used to decide which area received the PRP injection and which received a saline injection. Injections were given to each patient at one-week intervals. After 6 months the change in the patients’ hair density (number of hairs per square centimeter) and hair diameter (millimeters) was measured. The mean difference in hair density (PCP minus saline) was 59.47 hairs/cm2 and the mean difference in hair thickness was 0.08 mm.

What is the treatment?

Green Tea You wonder whether green tea lowers cholesterol.

To research the claim that green tea lowers LDL (so-called bad) cholesterol, you ask a random sample of individuals to divulge whether they are regular green tea users or not. You also obtain their LDL cholesterol levels. Finally, you compare the LDL cholesterol levels of the green tea drinkers to those of the non–green tea drinkers. Explain why this is an observational study.

Green Tea You wonder whether green tea lowers cholesterol.

Name some lurking variables that might exist in the study.

Green Tea You wonder whether green tea lowers cholesterol.

Explain how you woold use blinding in this experiment.

Green Tea You wonder whether green tea lowers cholesterol.

What factors might you attempt to control and fix at one level in this experiment?

Treatment for Osteoporosis Osteoporosis is a condition in which people experience decreased bone mass and an increase in the risk of bone fracture. Actonel is a drug that helps combat osteoporosis in postmenopausal women. In clinical trials, 1374 postmenopausal women were randomly divided into experimental and control groups. The subjects in the experimental group were administered 5 milligrams (mg) of Actonel, while the subjects in the control group were administered a placebo. The number of women who experienced a bone fracture over the course of one year was recorded. Of the 696 women in the experimental group, 27 experienced a fracture during the course of the year. Of the 678 women in the control group, 49 experienced a fracture during the course of the year.  

a. What type of experimental design is this? What is the response variable? Is it qualitative or quantitative? What are the treatments?  

Treatment for Osteoporosis Osteoporosis is a condition in which people experience decreased bone mass and an increase in the risk of bone fracture. Actonel is a drug that helps combat osteoporosis in postmenopausal women. In clinical trials, 1374 postmenopausal women were randomly divided into experimental and control groups. The subjects in the experimental group were administered 5 milligrams (mg) of Actonel, while the subjects in the control group were administered a placebo. The number of women who experienced a bone fracture over the course of one year was recorded. Of the 696 women in the experimental group, 27 experienced a fracture during the course of the year. Of the 678 women in the control group, 49 experienced a fracture during the course of the year.  

b. The experiment was double-blind. What does this mean?  

Researchers Katherine Tucker and associates wanted to determine whether consumption of cola is associated with lower bone mineral density. They looked at 1125 men and 1413 women in the Framingham Osteoporosis Study, which is a cohort that began in 1971. The first examination in this study began between 1971 and 1975, with participants returning for an examination every 4 years. Based on results of questionnaires, the researchers were able to determine cola consumption on a weekly basis. Analysis of the results indicated that women who consumed at least one cola per day (on average) had a bone mineral density that was significantly lower at the femoral neck than those who consumed less than one cola per day. The researchers did not find this relation in men.

Why is this a cohort study?

Researchers Katherine Tucker and associates wanted to determine whether consumption of cola is associated with lower bone mineral density. They looked at 1125 men and 1413 women in the Framingham Osteoporosis Study, which is a cohort that began in 1971. The first examination in this study began between 1971 and 1975, with participants returning for an examination every 4 years. Based on results of questionnaires, the researchers were able to determine cola consumption on a weekly basis. Analysis of the results indicated that women who consumed at least one cola per day (on average) had a bone mineral density that was significantly lower at the femoral neck than those who consumed less than one cola per day. The researchers did not find this relation in men.

What is the response variable in this study? What is the explanatory variable?