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The survey has bias. (a) Determine the type of bias. (b) Suggest a remedy. A newspaper article reported, "The Cosmopolitan magazine survey of more than 5000 Australian women aged \(18-34\) found about 42 percent considered themselves overweight or obese."

An ad for Crest Whitestrips Premium claims that the strips will whiten teeth in 7 days and the results will last for 12 months. A researcher who wishes to test this claim studies 20 sets of identical twins. Within each set of twins, one is randomly selected to use Crest Whitestrips Premium in addition to regular brushing and flossing, while the other just brushes and flosses. Whiteness of teeth is measured at the beginning of the study, after 7 days, and every month thereafter for 12 months. (a) What type of experimental design is this? (b) What is the response variable in this experiment? (c) What are the treatments? (d) What are other factors (controlled or uncontrolled) that could affect the response variable? (e) What might be an advantage of using identical twins as subjects in this experiment?

To help assess student learning in her developmental math courses, a mathematics professor at a community college implemented pre- and posttests for her students. A knowledge-gained score was obtained by taking the difference of the two test scores. (a) What type of experimental design is this? (b) What is the response variable in this experiment? (c) What is the treatment?

The survey has bias. (a) Determine the type of bias. (b) Suggest a remedy. A health teacher wants to research the weight of college students. She obtains the weights for all the students in her 9 A.M. class by looking at their driver's licenses or state IDs.

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 \((\mathrm{RT}),\) 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. (a) What type of experimental design is this? (b) What is the population being studied? (c) What is the response variable in this study? (d) What are the treatments? (e) Identify the experimental units. (f) Draw a diagram similar to Figure 7,8 , or 10 to illustrate the design.

The survey has bias. (a) Determine the type of bias. (b) Suggest a remedy. A magazine is conducting a study on the effects of infidelity in a marriage. The editors randomly select 400 women whose husbands were unfaithful and ask, "Do you believe a marriage can survive when the husband destroys the trust that must exist between husband and wife?"

Determine whether the study depicts an observational study or an experiment. Two hundred people are asked to perform a taste test in which they drink from two randomly placed, unmarked cups and asked which drink they prefer.

In Problems 11-22, identify the type of sampling used. A member of Congress wishes to determine her constituency's opinion regarding estate taxes. She divides her constituency into three income classes: low-income households. middle-income households, and upper-income households. She then takes a simple random sample of households from each income class.

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. (a) What type of experimental design is this? (b) What is the population being studied? (c) What is the response variable in this study? (d) What is the factor that is set to predetermined levels? What are the treatments? (e) Identify the experimental units. (f) What is the control group in this study? (g) Draw a diagram similar to Figure \(7,8,\) or 10 to illustrate the design.

Determine whether the study depicts an observational study or an experiment. Conservation agents netted 250 large-mouth bass in a lake and determined how many were carrying parasites.