Smoking Cessation in HIV Patients In a 2018 study reported in The Lancet, Mercie et al. investigated the efficacy and safety of varenicline for smoking cessation in people living with HIV. The study was a randomized, double-blind, placebo-controlled trial. Of the 123 subjects treated with varenicline, 18 abstained from smoking for the entire 48-week study period. Of the 124 subjects assigned to the placebo group, 8 abstained from smoking for the entire study period.
a. Find the sample percentage of subjects in each group who abstained from smoking for the entire study period.
b. Determine whether varenicline is effective in reducing smoking among HIV patients. Note that this means we should test if the proportion of the varenicline group who abstained from smoking for the entire study period is significantly greater than that of the placebo group. Use a significance level of
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Chapter 8 Solutions
Introductory Statistics
- "Does ginkgo improve memory?" The law allows marketers of herbs and other natural substances to make health claims that are not supported by evidence. Brands of ginkgo extract claim to "improve memory and concentration." A randomized experiment found some statistically significant evidence for such effects. The subjects were 250 healthy volunteers over 65 years old. They were randomly assigned to take ginkgo or a placebo pill (a dummy pill that looks and tastes the same). All the subjects took a battery of tests for learning and memory before treatment started and again after six weeks. a). The article said the study was double-blind. What does this mean in the context of this study? Be very specific on who's being blinded and explain why they should be blinded. b). You suspect physical fitness and mental fitness go hand-in-hand. Create a flow chart to describe a design for an experiment to include the confounding variable physical fitness. Be very specific in your design. Include all…arrow_forwardAs men age, their testosterone levels gradually decrease. This may cause a reduction in energy, an increase in fat, and other undesirable changes. Do testosterone supplements reverse some of these effects? A study in the Netherlands assigned 237 men aged 60 to 80 with low or low-normal testosterone levels to either a testosterone supplement or a placebo. Why is it necessary to include a control group in this experiment? Every experiment needs a control group in order to make proper comparisons between treatments. A control group is necessary to balance the effects of other variables among the treatment groups. A control group is necessary so any differences in the effects of the treatments can be distinguished from chance differences between the groups. A control group helps avoid confounding and reduces variability in the response variable. A control group is used to provide a baseline for comparing the effects of other treatments.arrow_forwardDoes heavy cell phone use affect brain activity? There is some concern about possible negative effects of radiofrequency signals delivered to the brain. In a randomized matched-pairs study, 47 healthy participants had cell phones placed on the left and right ears. Brain glucose metabolism (a measure of brain activity) was measured for all participants under two conditions: with one cell phone turned on for 50 minutes (the “on” condition) and with both cell phones off (the “off” condition). The amplitude of radio frequency waves emitted by the cell phones during the “on” condition was also measured. Is this an example of “paired-samples” or “independent samples”? The investigators were interested in seeing whether average brain glucose metabolism was different based on whether the cell phones were turned on or off. State the null and alternative hypotheses for this test. Suppose that the mean of differences ? is 0.8, ignoring the unit for now, and the standard deviation of the…arrow_forward
- A 2017 article in The New England Journal of Medicine details the results of a randomized clinical trial designed to evaluate the efficacy of a rotavirus gastroenteritis vaccine designed for infants. As per the authors: “Each year, rotavirus gastroenteritis is responsible for about 37% of deaths from diarrhea among children younger than 5 years of age worldwide, with a disproportionate effect in sub-Saharan Africa. We conducted a randomized, placebo-controlled trial in Niger to evaluate the efficacy of a live, oral bovine rotavirus pentavalent vaccine (BRV-PV, Serum Institute of India) to prevent severe rotavirus gastroenteritis. Healthy infants received three doses of the vaccine or placebo at 6, 10, and 14 weeks of age. Episodes of rotavirus gastroenteritis were assessed through active and passive surveillance.” The following Kaplan-Meier curves show the time to a diagnosis of rotavirus gastroenteritis separately for the vaccine and placebo samples. Infants were followed for up to 60…arrow_forwardFind the percent of women not experiencing any new UTIs in each of the three treatment groups.arrow_forward) Name one other limitation in this study (do not repeat any of the limitations you may have named above in your previous answers) and suggest how you would improve it.arrow_forward
- Does ginkgo improve memory? The law allows marketers of herbs and other natural substances to make health claims that are not supported by evidence. Brands of ginkgo extract claim to “improve memory and concentration.” A randomized comparative experiment found no statistically significant evidence for such effects. The subjects were 350 healthy volunteers over 60 years old. They were randomly assigned to ginkgo or a placebo pill (a dummy pill that looks and tastes the same). All the subjects took a battery of tests for learning and memory before treatment started and again after six weeks. (a) The study was double-blind. Why is this important? (b) Can the results of this study be generalized to a larger population? Can cause-and-effect be inferred? Explain. (c) Explain why it is advantageous to use 350 volunteers in this study, rather than, say, 30.arrow_forwardSubjects with pre-existing cardiovascular symptoms who were receiving subitramine, an appetite suppressant, were found to be at increased risk of cardiovascular events while taking the drug. The study included 9719 overweight or obese subjects with preexisting cardiovascular disease and/ or type 2 diabetes. The subjects were randomly assigned to subitramine (4787 subjects) or a placebo (4932 subjects) in a double-blind fashion. The primary outcome measured was the occurrence of any of the following events: nonfatal myocardial infarction or stroke, resuscitation after cardiac arrest, or cardiovascular death. The primary outcome was observed in 557 subjects in the subitramine group and 505 subjects in the placebo group. Do the data give good reason to think that there is a difference between the proportions of treatment and placebo subjects who experienced the primary outcome? (a) State hypotheses, find the test statistic and use either software or Table A for the P-value. Give both the…arrow_forwardCalcium and Blood Pressure Does increasing the amount of calcium in our diet reduce blood pressure? Examination of a large sample of people revealed a relationship between calcium intake and blood pressure. Such observational studies do not establish causation. Researchers therefore designed a randomized comparative experiment. The subjects were 21 healthy men who volunteered to take part in the experiment. They were randomly assigned to two groups: 10 of the men received a calcium supplement for 12 weeks, while the control group of 11 men received a placebo pill that looked identical. The experiment was double-blind. The response variable is the decrease in systolic (top number) blood pressure for a subject after 12 weeks, in millimeters of mercury. An increase appears as a negative number. Do the data provide convincing evidence that a calcium supplement reduces blood pressure more than a placebo, on average, for subjects like the ones in this study? Group 1 (calcium) Group (placebo)…arrow_forward
- When neither the subject nor those having contact with the subject know the treatment assignment, the study is called unbiased. double-blind. blind. statistically significant. randomized.arrow_forwardWhich type of experiment is a tightly controlled experiment in which an intervention is given to determine its effect on a certain disease or health condition? Animal study Experimental trial Epidemiological study Case control studyarrow_forwardA group of health conscious researchers were interested in ways to lower blood pressure. The study consisted of 90 participants. 30 participants were randomly assigned to eat a heart healthy diet, 30 were randomly assigned to a heart healthy exercise routine, and 30 were randomly assigned to do nothing and serve as a control. After a month of their assigned intervention, participants' blood pressure was measured. Which statistical test should be used to compare the 3 intervention types on post-treatment blood pressure? Select one: a. One-way between subjects ANOVA b. One-way repeated measures ANOVA Incorrect c. Two-way between subjects ANOVA d. None of these optionsarrow_forward