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What does it mean when an observational study is retrospective? What does it mean when an observational study is prospective?

A student entering a doctoral program in educational psychology is required to select two courses from the list of courses provided as part of his or her program. EPR 616, Research in Child Development EPR 630, Educational Research Planning and Interpretation EPR 631, Nonparametric Statistics EPR 632, Methods of Multivariate Analysis EPR 645, Theory of Measurement EPR 649, Fieldwork Methods in Educational Research EPR \(650,\) Interpretive Methods in Educational Research (a) List all possible two-course selections. (b) Comment on the likelihood that the pair of courses EPR 630 and EPR 645 will be selected.

Researchers wanted to determine the association between number of times one chews food and food consumption. They identified 45 individuals who were 18 to 45 years of age. First, the researchers determined a baseline for number of chews before swallowing food. Next, each participant attended three sessions to eat pizza for lunch until comfortably full by chewing each portion of food \(100 \%, 150 \%,\) and \(200 \%\) of their baseline number of chews before swallowing. Food intake for each of the three chewing treatments was then measured. It was found that food consumption was reduced significantly, by \(9.5 \%\) and \(14.8 \%,\) respectively, for the \(150 \%\) and \(200 \%\) number of chews compared to the baseline. (a) What is the research objective of the study? (b) What is the response variable in this study? Is it quantitative or qualitative? (c) What is the explanatory variable in this study? Is it quantitative or qualitative? (d) Who are the experimental units? (e) How is control used in this study? (f) Each individual chewed \(100 \%, 150 \%,\) and \(200 \%\) of their baseline number of chews before swallowing. This is referred to as a repeated-measures study since the same participants were exposed to each treatment. The order in which chewing took place ( \(100 \%\) versus \(150 \%\) versus \(200 \%\) ) was determined randomly. Explain why this is important.

When conducting a cluster sample, it is better to have fewer clusters with more individuals when the clusters are heterogeneous.

Determine whether the underlined value is a parameter or a statistic. The average score for a class of 28 students taking a calculus midterm exam was \(72 \%\).

To determine if topiramate is a safe and effective treatment for alcohol dependence, researchers conducted a 14 -week trial of 371 men and women aged 18 to 65 years diagnosed with alcohol dependence. In this double-blind, randomized, placebo-controlled experiment, subjects were randomly given either 300 milligrams (mg) of topiramate (183 subjects) or a placebo (188 subjects) daily, along with a weekly compliance enhancement intervention. The variable used to determine the effectiveness of the treatment was self-reported percentage of heavy drinking days. Results indicated that topiramate was more effective than placebo at reducing the percentage of heavy drinking days. The researchers concluded that topiramate is a promising treatment for alcohol dependence. (a) What does it mean for the experiment to be placebocontrolled? (b) What does it mean for the experiment to be double-blind? Why do you think it is necessary for the experiment to be double-blind? (c) What does it mean for the experiment to be randomized? (d) What is the population for which this study applies? What is the sample? (e) What are the treatments? (f) What is the response variable?

The survey has bias. (a) Determine the type of bias. (b) Suggest a remedy. A polling organization conducts a study to estimate the percentage of households that speaks a foreign language as the primary language. It mails a questionnaire to 1023 randomly selected households throughout the United States and asks the head of household if a foreign language is the primary language spoken in the home. Of the 1023 households selected, 12 responded.

Inferences based on voluntary response samples are generally not reliable.

A pharmaceutical company has developed an experimental drug meant to relieve symptoms associated with the common cold. The company identifies 300 adult males 25 to 29 years old who have a common cold and randomly divides them into two groups. Group 1 is given the experimental drug, while group 2 is given a placebo. After 1 week of treatment, the proportion that still have cold symptoms in each group are compared. (a) What is the response variable in this experiment? (b) Think of some of the factors in the study. How are they controlled? (c) What are the treatments? How many treatments are there? (d) How are the factors that are not controlled dealt with? (e) What type of experimental design is this? (f) Identify the subjects. (g) Draw a diagram similar to Figure \(7,8,\) or 10 to illustrate the design.

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?