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A company wants to test the effectiveness of a new acne cream. The company recruits 500 girls ages 13 to 17 who have acne. The subjects are randomly assigned into two groups. One group is given the acne cream and the other is given a placebo that looks exactly like the acne cream. Both groups apply the cream daily for two months. Facial photos are taken at the beginning and end of the treatment to compare results.

b. Identify a potential problem with the experimental design being used and suggest a way to improve it.

A company wants to test the effectiveness of a new acne cream. The company recruits 500 girls ages 13 to 17 who have acne. The subjects are randomly assigned into two groups. One group is given the acne cream and the other is given a placebo that looks exactly like the acne cream. Both groups apply the cream daily for two months. Facial photos are taken at the beginning and end of the treatment to compare results.

c. How could this experiment be designed to be double-blind?

Researchers in Japan tested the effect of cannabidiol (CBD) in treating late teenagers with social anxiety disorder (SAD). Thirty-seven 18- to 19-year-old teenagers with SAD took part in the study. The patients were assigned at random to receive a daily dose of either CBD or a placebo for 4 weeks. Symptoms were measured using The Fear of Negative Evaluation Questionnaire and the Liebowitz Social Anxiety Scale at the beginning and end of the treatment. (Source: Frontiers in Psychology)

a. Identify the experimental units and treatments used in this experiment.

Identify the sampling technique used, and discuss potential sources of bias (if any). Explain.

Questioning university students as they leave a college cafeteria, a researcher asks 342 students about their eating habits.

Identify the sampling technique used, and discuss potential sources of bias (if any). Explain.

Soybeans are planted on a 48-acre field. The field is divided into one-acre subplots. A sample is taken from each subplot to estimate the harvest.

Determine whether you would take a census or use a sampling. If you would use a sampling, determine which sampling technique you would use. Explain.

The average GPA of the 85 students on a college football team roster

Determine whether you would take a census or use a sampling. If you would use a sampling, determine which sampling technique you would use. Explain.

The average distance traveled to a stadium by 55,000 spectators

Determine whether the survey question is biased. If the question is biased, suggest a better wording.

How much do you exercise during an average week?

Determine whether the survey question is biased. If the question is biased, suggest a better wording.

How does the media influence the opinions of voters?

Identify the population and the sample. Describe the sample data set.

Eighty-three doctors working in the St. Louis area were surveyed concerning their opinions on health care reform.

Determine whether the number describes a population parameter or a sample statistic. Explain your reasoning.

In a survey of 1000 household food purchasers, 24.7% say that they avoid meat, dairy, and eggs produced by animals living in confined conditions. (Source: FoodPrint)

Which part of the survey described in Exercise 3 represents the descriptive branch of statistics? Make an inference based on the results of the survey.

Determine whether the data are qualitative or quantitative. Explain your reasoning.

The zip codes of a sample of 200 customers at a sporting goods store

Determine whether the data are qualitative or quantitative. Explain your reasoning.

The marital statuses of the employees of a casino

Determine the level of measurement of the data set. Explain.

The total compensations (in millions of dollars) of the ten highest-paid CEOs at U.S. public companies are listed. (Source: 24/7 Wall St.)

280.6 66.9 42.9 36.5 34.3 31.6 31.6 28.8 26.4 25.8