A new study evaluates the effect of a novel antibiotic, compound A, in treating urinary tract infections in children. Children and adolescents with a confirmed urinary tract infection are randomized to receive either compound A or trimethoprim-sulfamethoxazole. The outcome of interest is microbiologic cure at day 3 of therapy.

Of the following, the BEST statement of a null hypothesis with regard to this study is that at 3 days, compound A

A researcher is interested in studying the effects of preterm birth on math and reading achievement. She plans to recruit children ages 6 to 12 years with a history of preterm birth who have a term-born sibling within the same age range to serve as a matched control.

Of the following, the use of a term-born sibling to serve as a matched control is BEST described as a means of minimizing

A researcher is developing a double-blind, placebo-controlled, parallel-group randomized controlled trial assessing the effect of a new leukotriene receptor antagonist on forced expiratory volume in the first second (FEV1) rounded to the nearest 0.1 liter.

Of the following, the BEST statistical test to compare the FEV1 between the 2 groups (new drug vs placebo) at the end of this study is

The medical director of a large neonatal intensive care service discovers that about half of the medical records she reviewed lacked a graphic growth chart, contrary to unit protocol. Several of her colleagues thought that plotting daily growth parameters on paper became unnecessary since the advent of an electronic records system. Nevertheless, she hypothesized that weight gain might be enhanced with the use of such graphs and proposed studying the question.

She designed a retrospective study of consecutive admissions of premature infants who met the following criteria: born after the advent of electronic charting, hospital stay of at least 21 days, no congenital infection or anomaly, and no enterocolitis. She proposed examining the charts of 100 such infants. The presence or absence of a growth chart would be noted as well as the average daily weight gain during the second and third weeks after birth in terms of grams per kilogram of birthweight per day. She believes that weight gain will have an approximately normal distribution.

Of the following, the MOST appropriate statistical test to be used to address the hypothesis is

A nephrology fellow wants to assess the prevalence of influenza in vaccinated and unvaccinated children 8 to 15 years of age with nephrotic syndrome, chronic kidney disease, and kidney transplant recipients during the upcoming winter season. His hypothesis is that the vaccine will be associated with a lower prevalence of influenza infection in the 3 groups.

Of the following, the MOST appropriate statistical test to analyze the results is

A researcher is designing a study to look at parent preferences in the treatment of juvenile arthritis. Parents will be asked to fill out a survey with the factors that are involved in their choice of treatment, and factors will be ranked and compared with medical staff responses. The hypothesis is that parent factors in treatment decision-making are different from medical staff factors.

Of the following, the BEST statistical test to evaluate this hypothesis is

A physician is reviewing a journal article with a group of medical students. The article describes a randomized controlled trial comparing 2 warm-up exercise programs designed to prevent knee injuries in high school soccer athletes. The researchers found that 5% of the athletes who participated in a strengthening warm-up program sustained knee injuries during their soccer season compared to 15% of control group participants who used a static stretching warm-up program. The researchers concluded that for every 10 athletes who participated in the strengthening program, there was 1 fewer injury.

Of the following, the CONCEPT expressed in this last conclusion is known as

A 6-year-old girl with a deep vein thrombosis is treated with twice-daily injectable anticoagulants, which is the standard of care. Her parents report that every time she receives a dose of the drug, she screams and cries hysterically and will push, punch, and bite her parents as they try to give her the injection. In researching possible alternative treatments, the pediatrician identifies a large, randomized controlled, clinical trial in which the injectable standard-of-care drug was compared with a once-daily oral anticoagulant approved by the US Food and Drug Administration. There was no statistical difference in efficacy between the two therapeutic options. However, the rate of bleeding complications was 0.5% in the oral anticoagulant group vs 0.3% in the standard-of-care injectable drug group (p = .04).

Of the following, the MOST accurate statement about the use of the oral anticoagulant for this patient is that it

A researcher is evaluating a new agent for the treatment of patent ductus arteriosus (PDA) in very-low-birthweight neonates. The researcher has collected data on 100 neonates with PDA. Of 50 neonates treated with a traditional agent, 13 responded, and of the 50 neonates taking the new agent, 18 responded. A Chi-square test is performed for independence and P = .28. The researcher concludes that there is no difference in the response to the two drugs. Several months later, a large multicenter trial is published that demonstrates efficacy of the new drug.

Of the following, the MOST likely statistical error the researcher has committed is

Dr. Bone hypothesizes that a new biologic medication, unobtainimab, will be effective for the treatment of pediatric systemic lupus erythematosus (SLE). Dr. Bone’s research team performs a randomized, double-blind study comparing unobtainimab to placebo in adolescents with SLE. The primary outcome is SLE Disease Activity Index (SLEDAI) scores. Twenty patients who have severe organ involvement and for whom cyclophosphamide treatment has been unsuccessful are recruited. Subjects are randomized into 2 groups: 10 patients receive 8 twice-monthly infusions of unobtainimab and 10 patients receive twice-monthly intravenous normal saline as placebo. Subjects are followed for 3 months after completing the course of unobtainimab or placebo. No significant difference in SLEDAI scores is noted. Dr. Bone’s group publishes the findings, concluding that unobtainimab is no more effective than placebo for adolescents with SLE.

One year later, an international collaborative group headed by Dr. Joint publishes a much larger study (N = 893) that examines unobtainimab for the treatment of SLE in adolescents and uses SLEDAI scores as the primary outcome. Patients recently diagnosed with SLE are randomized to receive treatment with either unobtainimab or mycophenolate. This study shows a 28% benefit in overall SLEDAI scores at 6 months in subjects taking unobtainimab compared with the standard treatment group (P = 0.004). This study is published in a highly regarded journal, and the findings are later confirmed in other studies.

Of the following, Dr. Bone’s conclusion that unobtainimab is no more effective than placebo is BEST characterized as