Researchers use active-controlled trials to test new medications that are used to treat a particular illness against old medications used to treat the same illness.
The level of significance is the probability that we reject the null hypothesis (in favor of the alternative) when it is actually true.
Randomization in a clinical trial is defined as which of the following?
If a 90% confidence interval for the mean is (75.3 to 80.9), we would reject H0: m =70 in favor of H1:m≠ 70 ata= 0.05.
If a test is run and p = 0.0356, then we can reject H0 ata= 0.01.
It is important for researchers to account for attrition or loss of participants during follow-up.
Assuming 50,000 individuals in the United States are diagnosed every year, and of those individuals diagnosed with HIV each year, approximately 33,500 individuals diagnosed with HIV are gay or bisexual males. What prevalence of the new HIV cases are from members of the population of gay or bisexual males?
The margin of error is always greater than or equal to the standard error.
Which of the following individuals is likely to be excluded from a clinical trial?
Assume a doctor uses a specific form of mesh to repair all hernias in his hernia patients. The makers of the mesh found there was an error that occurred while making the mesh, and the hernia mesh has a 45% chance of failure. The doctor has treated 7 patients with the mesh so far; thus, the probability that the mesh does not fail in all seven patients is .0152.
A researcher wants to compare the mean concentration of two medications considered biologically equivalent, i.e., two medications that are able to produce the same therapeutic effect at the same level of concentration in the blood. The group of individuals on medication one (n = 32) had a mean blood concentration of 21.7 micrograms per milliliter with a standard deviation of 8.7 micrograms per milliliter. The group of individuals on medication two (n = 32) had a mean blood concentration of 19.4 micrograms per milliliter with a standard deviation of 5.2 micrograms per milliliter. Construct and interpret a 95% confidence interval demonstrating the difference in means for the individuals on medication one when compared to the group of individuals on medication two.
In logistic regression, the predictors are dichotomous, and the outcome is a continuous variable.
Ethnicity is best described as which type of variable?
The level of significance alpha most commonly used are: 0.01, 0.05, 0.1.
When performing a Mann-Whitney U test, one should always use the higher value of the calculated U values to compare to the critical U value while making the decision rule.
A stratified random sample can be used to ensure underrepresented populations are represented in a study.
Considering the data blow. The mean is 118.44.
A researcher wants to determine the sensitivity of mammograms to determine how effective they are at diagnosing women who have breast cancer. Assume the researcher obtained the above results from a study, calculate and interpret the sensitivity of mammograms for detecting breast cancer.
A researcher notes that there seems to be a difference in the prevalence of high blood pressure among college-educated individuals who consume low amounts of processed foods and the prevalence of individuals who only have a high school education and consume high amounts of processed foods. Use the appropriate hypothesis to test for the independence of the two independent variables presented here at the 5% significance level to ensure confounding has not influenced the study’s results. Then, interpret your response.
A researcher decides to take a random sample of the population and determine the ALT levels of the population, which fall on a continuum. A bar chart would be useful in determining if the ALT levels of the population are normally distributed.
If a 95% confidence interval for the difference in two independent means is (-4.5 to 2.1), then the point estimate is -2.1.
If a 95% confidence interval for the difference in two independent means is (2.1 to 4.5), there is no significant difference in means.
An r value of .8 indicates a strong positive correlation.
Considering the data blow. The median is 120. 100 120 111 115 120 116 125 129 130
A clinical trial is conducted to compare an experimental medication to placebo to reduce the symptoms of asthma. Two hundred participants are enrolled in the study and randomized to receive either the experimental medication or placebo. The primary outcome is self-reported reduction of symptoms. Among 100 participants who receive the experimental medication, 38 report a reduction of symptoms as compared to 21 participants of 100 assigned to placebo. When you test if there is a significant difference in the proportions of participants reporting a reduction of symptoms between the experimental and placebo groups. Use α = 0.05. What should the researcher’s conclusion be for a 5% significance level? Reject H0
because 2.64 ≥ 1.960. We have statistically significant evidence at α = 0.05 to show that there is a difference in the proportions of patients reporting a reduction in symptoms.
A clinical trial is being conducted in order to determine the efficacy of a new drug used to treat Rheumatoid arthritis. The efficacy of the medication will not only be determined by the physical improvement of symptoms but also by using a blood test to examine the concentration C-reactive protein (an inflammatory marker) in an individual’s blood. If the researcher wants a margin of error for the level of C- reactive protein to be less than or equal to 3.0 mg/dL, and if the standard deviation for C-reactive protein concentrations among arthritis patients was previously documented at 8 mg/dL, how many patients should be recruited for each group in the study assuming a 95% confidence interval will be used to quantify the mean differences between the control group and the treatment group?
The sample size required to detect an effect size of 0.25 is larger than the sample size required to detect an effect size of 0.50 with 80% power and a 5% level of significance.
The following are body mass index (BMI) scores measured in 12 patients who are free of diabetes and are participating in a study of risk factors for obesity. Body mass index is measured as the ratio of weight in kilograms to height in meters squared. Generate a 95% confidence interval estimate of the true BMI.
How many subjects would be needed to ensure that a 95% confidence interval estimate of BMI had a margin of error not exceeding 3 units?
Based on the data set below, what is the standard deviation?
Peak expiratory flow (PEF) is a measure of a patient’s ability to expel air from the lungs. Patients with asthma or other respiratory conditions often have restricted PEF. The mean PEF for children free of asthma is 306. An investigator wants to test whether children with chronic bronchitis have restricted PEF. A sample of 50 children with chronic bronchitis is studied, and their mean PEF is 251 with a standard deviation of 71. When you run the appropriate test at α = 0.05, the appropriate conclusion to whether there statistical evidence of a lower mean PEF in children with chronic bronchitis is?
Peak expiratory flow (PEF) is a measure of a patient’s ability to expel air from the lungs. Patients with asthma or other respiratory conditions often have restricted PEF. The mean PEF for children free of asthma is 306. An investigator conducts a study to investigate whether there is a difference in mean PEF in children with chronic bronchitis as compared to those without asthma or other respiratory conditions that often have restricted PEF. Data on PEF are collected and summarized below. Based on the data, is there statistical evidence of a lower mean PEF in children with chronic bronchitis as compared to those without? Run the appropriate test at α = 0.05.
A clinical trial is run to investigate the effectiveness of an experimental drug in reducing preterm delivery to a drug considered standard care and to a placebo. Pregnant women are enrolled and randomly assigned to receive either the experimental drug, the standard drug or a placebo. Women are followed through delivery and classified as delivering preterm (< 37 weeks) or not. The data are shown below.
A study is run comparing HDL cholesterol levels between men who exercise regularly and those who do not. The data are shown below.
Suppose a hypertension trial is mounted and 18 participants are randomly assigned to one of the comparison treatments. Each participant takes the assigned medication and his or her systolic blood pressure is recorded after 6 months on the assigned treatment. The data are as follows.
A study is designed to investigate whether there is a difference in response to various treatments in patients with Rheumatoid arthritis. The outcome is the patient’s self-reported effect of treatment. The data are shown below. Is there a significant difference in the effect of treatment? Run the test at a 5% level of significance.
Using the data below, suppose we focus on the proportions of patients who show improvement. Is there a statistically significant difference in the proportions of patients who show improvement between treatments 1 and 2. Run the test at a 5% level of significance.
An analysis is conducted to compare mean time to pain relief (measured in minutes) under four competing treatment regimens. Summary statistics on the four treatments are shown below.
A small pilot study is conducted to investigate the effect of a nutritional supplement on total body weight. Six participants agree to take the nutritional supplement. To assess its effect on body weight, weights are measured before starting the supplementation and then after 6 weeks. The data are shown below. Is there a significant increase in body weight following supplementation? Run the test at a 5% level of significance.
A small pilot study is run to compare a new drug for chronic pain to one that is currently available. Participants are randomly assigned to receive either the new drug or the currently available drug and to report improvement in pain on a 5-point ordinal scale: 1 = Pain is much worse, 2 = Pain is slightly worse, 3 = No change, 4 = Pain improved slightly, 5 = Pain much improved. Is there a significant difference in self-reported improvement in pain? Use the Mann-Whitney U test with a 5% level of significance.
The following table was presented in an article summarizing a study to compare a new drug to a standard drug and to a placebo.
What is the appropriate statistical test to assess whether there is an association between obesity status (normal weight, overweight, obese) and 5-year incident cardiovascular disease (CVD)? Suppose each participant’s obesity status (category) is known along with whether they develop CVD over the next 5 years or not.
A random sample of 8 adults aged 30 years were asked how much they spent on medical costs in the year 2009. Using the following data, compute the sample mean, the sample standard deviation, the sample median, and the first and third quartiles.
The table below summarizes baseline characteristics of patients participating in a clinical trial. a) Are there any statistically significant differences in baseline characteristics between treatment groups? Justify your answer.