A study (Journal of Family Practice 2000; 50:138-144) with 233 low-income adult smokers evaluated the effectiveness of usual care (physician advice and follow-up) for smokers wishing to quit to the usual care enhanced by computer-assisted telephone counseling sessions. Each subject was assigned randomly either to the usual care or to the usual care plus counseling, and their smoking status (still smoking or quit smoking) was observed after 3 months. The percentage who had quit smoking was higher for the group receiving counseling. (a) Identify the response variable and the explanatory variable. Response:  ---Select--- type of care  income level  quit smoking or not  time until quit smoking Explanatory:  ---Select--- type of care  income level  quit smoking or not  time until quit smoking (b) Is this study an observational study or an experiment? Explain.   Observational study. Smokers were not randomly assigned to care groups. Observational study. Smokers were randomly assigned to care groups.     Experiment. Smokers were randomly assigned to care groups. Experiment. Smokers were not randomly assigned to care groups. (c) How does the design of this study take into account potential lurking variables? By randomly assigning subjects to the treatment groups. By taking a large sample (n = 233).     By monitoring the subjects for a long period (3 months). By assigning subjects to receive both treatments.

Researchers investigate how the presence of cell phones influence the quality of human interaction.  Subjects are randomly selected from a population and divided into an experimental group that is asked to leave their phones in the front of the room and a control group that are not asked to leave their cell phones at the front of the room.  Subjects are left alone for 10 minutes and then asked to take a survey designed to measure quality of interactions they had with others in the experiment.  What statistical test is appropriate?

Mental Health A study was performed looking at the effect of physical activity on cognitive function among adults at high risk for Alzheimer's disease. There were 170 eligible subjects randomly assigned to either an exercise intervention (exercise group) or a control intervention (control group). The subjects were followed at 6-month intervals up to 18 months of follow-up. The primary assessment scale was the Alzheimer's Disease Assessment Scale-Cognitive Subscale (ADAS-Cog). The results at 18 months of follow-up among participants with mild cognitive impairment are given in the table below. (Let population 1 be the exercise group and population 2 be the control group. Use exercise group control group.) Mean difference from baseline (18-month score minus baseline score) among participants with mild cognitive impairment in the ADAS-Cog score* Mean change 95% CI n H₁: Exercise group Control group USE SALT -0.37 (-1.37, 0.63) 48 -0.43 (-1.35, 0.49) 52 (a) What is the standard deviation of…

st is 22. Oishi and Shigehiro (2010) report that people who move from home to home frequently as children tend to have lower than average levels of well-being as adults. To further examine this relationship, a psychologist obtains a sample of n = 12 young adults who each experienced 5 or more different homes before they were 16 years old. These participants were given a standardized well-being questionnaire for which the general population has a