Commonly used vaccines for influenza are trivalent and contain only one type of influenza B virus. They may be ineffective against other types of influenza B virus. A randomized clinical trial was performed among children 3 to 8 years of age in 8 countries. Children received either a quadrivalent vaccine (QIV) that had more than one influenza B virus or a trivalent Hepatitis A vaccine (control) (Jain, et al., [9]. New England Journal of Medicine 2013: 369(26): 2481–2491). An attack rate (i.e.,% of children who developed influenza) starting 14 days after vaccination until the end of the study was computed for each vaccine group, stratified by age. The following data were reported:
Table 3.7 Attack rate for influenza by age and treatment group
Suppose 3 children in a village ages 3, 5, and 7 are vaccinated with the QIV vaccine. What is the probability that at least one child among the 3 will get influenza?
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Chapter 3 Solutions
Fundamentals of Biostatistics
- What is an experiment?arrow_forwardAn article from the American Journal of Public Health reports the results from a randomized study designed to evaluate the efficacy of an intervention targeted to Hispanic/Latino men who identify as gay, bi-sexual or other men who have sex with men (MSM). A representative sample of 254 such men was randomized to be in either the intervention group (n=152, with 141 ultimately participating in the study) or the control group (n=152, with 147 ulitmately participating in the study). The primary outcome under study getting tested for HIV within the six-months following group assignment (randomization) among those who had been sexually active in this same six-month follow-up period. At six months of follow-up, 141 subjects in the intervention group reported having had sex (with men and/or women) since randomization. Of these 141 men, 114 had been tested for HIV since being randomized. At six months of follow-up, 147 subjects in the control group reported having had sex (with men…arrow_forwardA 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_forward
- The article “Capillary Leak Syndrome in Children with C4A-Deficiency Undergoing Cardiac Surgery with Cardiopulmonary Bypass: A Double-Blind, Randomised Controlled Study” (S. Zhang, S. Wang, et al., Lancet, 2005:556–562) presents the results of a study of the effectiveness of giving blood plasma containing complement component C4A to pediatric cardiopulmonary bypass patients. Of 58 patients receiving C4A-rich plasma, the average length of hospital stay was 8.5 days and the standard deviation was 1.9 days. Of 58 patients receiving C4A-free plasma, the average length of hospital stay was 11.9 days and the standard deviation was 3.6 days. Can you conclude that the mean hospital stay is shorter for patients receiving C4A-rich plasma?arrow_forwardThe May 10, 2007 issue of The New England Journal of Medicine describes two large randomized, placebo-controlled trials of a vaccine for HPV-related cancer. HPV is human papillomavirus, the most common form of sexually transmitted infection. For the group of people who received the vaccine, the HPV-related cancer rate was much lower than for those who received a placebo. Which best describes the goal of this study?arrow_forwardA consumer advocacy group wanted to study whether different airline carriers differed in terms of their delayed flights. In particular, the researchers were interested in the relationship between p1, the proportion of Alpha Airlines flights that were delayed at least 15 minutes, and p2, the proportion of Beta Airlines flights that were delayed at least 15 minutes. A random sample of 1,000 Alpha flights and a separate random sample of 1,000 Beta flights found that 67 of the Alpha fights and 160 of the Beta flights were delayed at least 15 minutes. The conditions for inference were checked and verified. Does this set of samples provide strong evidence that Alpha Airlines has a smaller proportion of flights that are delayed at least 15 minutes than Beta Airlines, at the α = 0.05 significance level? Find the z-table here. A. The test statistic is z = –6.56 and the P-value ≈ 0. Since the P-value ≈ 0 < 0.05, there is not sufficient evidence that Alpha Airlines has fewer delayed…arrow_forward
- A prospective study on the relationship between aspirin use and heart attacks by the Physicians’ Health Study Research Group at Harvard Medical School is presented below. The Physicians’ Health Study was a 5-year randomized study of whether regular aspirin intake reduces risk of myocardial infarction or heart attack. Every other day, physicians participating in the study took either one aspirin tablet or a placebo. The study was blind ---those in the study did not know whether they were taking aspirin or a placebo. Of the 11,034 physicians taking a placebo, 189 suffered heart attacks over the course of the study, whereas of the 11,037 taking aspirin, 104 had heart attacks. Can we say that the intake of aspirin appears to diminish the risk of myocardial infarction? LOOK AT THE IMAGE (table) THAT I ATTACHED Let patients taking placebo be the first group and those taking aspirin in the second group. Calculate the following and make an interpretation: confidence interval for risk…arrow_forwardIn a clinical trial of Nasonex, 300 allergy patients were randomized into two groups, with Group 1 receiving the Nasonex drug (200 mg) and Group 2 receiving a placebo. The experimenter used a 2:1 randomization plan so that more subjects would be assigned to the Nasonex group. One outcome of interest is the incidence rate of headache as a side-effect. Of the 200 patients randomized to the Nasonex group, 52 (or 26%) reported experiencing a headache; and of the 100 patients randomized to the placebo group, only 22 (22%) reported a headache. 1. The makers of Nasonex are concerned that their allergy medication might increase the incidence of headaches. So they would like to assess the claim that the incidence rate of headaches is higher for Nasonex users as compared to placebo. So the null hypothesis is given by H0: p1 - p2 = 0. Select the appropriate alternative hypothesis. Ha: p1 - p2 ≠ 0 Ha: p1 - p2 > 0 Ha: p1 - p2 < 0 2. It seems that the sample sizes of 200…arrow_forwardElizon Pharmaceuticals, Inc., announced the results of its first human trial of NPI 32101, a topical form of its skin ointment. A total of 225 patients diagnosed with skin irritations were randomly divided into three groups as part of a double-blind, placebo-controlled study to test the effectiveness of the new topical cream. The first group received a 0.5% cream, the second group received a 1.0% cream, and the third group received a placebo. Groups were treated twice daily for a 6-week period. (a)What type of experimental design is this? (b)What is the control group for this study? (c)What is the factor that is set to predetermined levels? What is the treatment? (d)What does it mean for this study to be double-blind? (e)Identify the experimental units. (f)Draw a diagram to illustrate the design.arrow_forward
- The results of a multicenter clinical trial to determine the safety and efficacy of the pancreatic lipase inhibitor, Xenical, was reported (Ingersoll, 1997). Xenical is used to block the absorption of dietary fat. The article reported that more than 4000 patients in the U.S. and Europe were randomized to receive Xenical or a placebo in a parallel groups study. After one year, 57% of those receiving Xenical had lost at least 5% of their body weight, as opposed to 31% of those receiving a placebo. Assume that exactly 4000 patients were in the study, and that 2000 were randomized to receive a placebo and 2000 received Xenical. Please Compute a 95% confidence interval for the “relative risk” of losing at least 5% of body weight for those receiving Xenical relative to those receiving placebo. Can the drug be considered effective?arrow_forwardA randomized study was performed to determine whether a diet of processed meats causes a higher proportion of incidents of breast cancer. Researchers compared high intake versus low intake diets of processed meats for women with breast cancer and found the following results shown in the two-way table below: Breast Cancer No Breast Cancer Total High Intake processed meat 93 157 250 Low Intake processed meat 67 163 230 Conduct a hypothesis test for this problem, using for the proportion with diet high in processed meat who got breast cancer and for the proportion of women with diet low in processed meat who got breast cancer. PLEASE HELP WITH THE FOLLOWING - Find the p-value. Write generic conclusion. Write conclusion in context.arrow_forwardBeard et al. (Lancet, 1982:455) described a randomised trial to determine if a low sodium diet was an effective substitute for pharmacological control of hypertension. 90 patients on medication for mild hypertension were allocated at random into two groups. The 45 participants in the intervention group (diet group) were encouraged to adopt a diet free from sodium. The other 45 participants (control group) were asked to continue their usual diet. All the participants were kept under close surveillance to see if it was possible to discontinue the medication for hypertension without detriment. In the diet group, medication was discontinued for 14 participants and in the control group for 4 participants.a) Draw a 2 by 2 table .b) Carry out a significance test to compare the intervention (diet group) and control group with respect to discontinuation of medication for hypertension.c) Write a brief report on your conclusion.arrow_forward