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
Trending nowThis is a popular solution!
Chapter 8 Solutions
INTRODUCTORY STATISTICS (LOOSELEAF)
- As 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_forwardMost alpine skiers and snowboarders do not use helmets. Do helmetsreduce the risk of head injuries? A study in Norway compared skiers and snowboarders who suffered head injuries with a control group who were not injured. Of 578 injured subjects, 96 had worn a helmet. Of the 2992 in the control group, 656 wore helmets. Is helmet use less common among skiers and snowboarders who have head injuries?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_forwardHomechooling has become very popular in the United States, and many colleges try to attract students from this group. Evidence suggests that approximately 90% of all homeschooled children attend college. To check this claim, a random sample of 208 homeschooled children was obtained, and 180 of them were found to have attended college. The researcher wishes to determine whether the proportion of homeschool children who attend college is different from 0.90. Test an appropriate hypothesis and state your conclusion. Make sure to state and check all conditions and state your conclusion in context.arrow_forwardThe researchers sought to explore the connection between dietary fat consumption and the incidence of cardiovascular disease (CVD) events in a cohort of 5,115 young adults of both Black and White backgrounds. In 1985, these individuals underwent an initial examination. Over the subsequent 35 years, those who were initially free of disease were monitored to investigate the potential associations between their dietary fat intake and the occurrence of CVD events. Among the 2,100 young adults who had a high-fat diet at the start of the study, 255 experienced a new CVD event. Among the 3,015 young adults who did not have a high-fat diet at baseline, 125 experienced a new CVD event during the follow-up period. Risk of CVD events among those with a high-fat diet is ____. Risk of CVD events among those without a high-fat is ____. The relative risk is ____.arrow_forward
- Subjects 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_forwardWhen 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_forward