MBA 503 University of Maryland University College Statistics Worksheet
QUESTION 1 The margin of error is always greater than or equal to the standard error. True False 3.4 points QUESTION 2 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? n for the treatment group = 112; n for the control group = 111 n for the treatment group = 56; n for the control group = 57 n for the treatment group = 55; n for the control group = 55 n for the treatment group = 112; n for the control group = 112 3.4 points QUESTION 3 It is important for researchers to account for attrition or loss of participants during follow-up. True False 3.4 points QUESTION 4 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. True False 3.4 points QUESTION 5 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. True False 3.4 points QUESTION 6 Which of the following individuals is likely to be excluded from a clinical trial? An individual with other diseases besides the disease of interest. An individual whose data is considered to be an outlier. An individual of who is considered to be a minority. An individual who will have difficulty complying trial protocols. 3.4 points QUESTION 7 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. Diet Low in Processed Foods Normal BP High BP Total College Education 124 55 179 High School Education 69 152 221 Total 193 207 400 Diet High in Processed Foods Normal BP High BP Total College Education 64 85 149 High School Education 98 153 251 Total 162 238 400 The chi square value of 37.724 is higher than the chi square value of 3.84; therefore, we do not reject H0 at the 5% level and reject H1, which states that level of education and the amount of processed foods in an individual’s diet are not independent of one another. The chi square value of 37.724 is higher than the chi square value of 3.84; therefore, we do not reject H0 at the 5% level and reject H1, which states that level of education and the incidence of high blood pressure are not independent of one another. The chi square value of 37.724 is higher than the chi square value of 3.84; therefore, we can reject H0 at the 5% level in favor of H1, which states that level of education and the incidence of high blood pressure are not independent of one another. The chi square value of 37.724 is higher than the chi square value of 3.84; therefore, we can reject H0 at the 5% level in favor of H1, which states that level of education and the amount of processed foods in an individual’s diet are not independent of one another. 3.4 points QUESTION 8 If a test is run and p = 0.0356, then we can reject H0 at a = 0.01. True False 3.4 points QUESTION 9 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. True False 3.4 points QUESTION 10 In logistic regression, the predictors are dichotomous, and the outcome is a continuous variable. True False 3.4 points QUESTION 11 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. True False 3.4 points QUESTION 12 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. True False 3.4 points QUESTION 13 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. The researchers are 95% confident that the true mean difference in medication concentration levels between individuals on medication one and individuals on medication two is between 4.867 micrograms per milliliter and 9.467 micrograms per milliliter. The researchers are 95% confident that the true mean difference in medication concentration levels between individuals on medication one and individuals on medication two is between -1.212 micrograms per milliliter and 5.812 micrograms per milliliter. The researchers are 95% confident that the true mean difference in medication concentration levels between individuals on medication one and individuals on medication two is between 11.747 micrograms per milliliter and 16.347 micrograms per milliliter. The researchers are 95% confident that the true mean difference in medication concentration levels between individuals on medication one and individuals on medication two is between 3.477 micrograms per milliliter and 8.077 micrograms per milliliter. 3.4 points QUESTION 14 Considering the data blow. The mean is 118.44. 100 120 111 115 120 116 125 129 130 True False 3.4 points QUESTION 15 Randomization in a clinical trial is defined as which of the following? The process by which individuals are coupled into groups for comparison in order to minimize bias and confounding. The process by which individuals are assigned a number and are selected through the usage of a pattern which minimizes bias and confounding. The process by which individuals are randomly assigned to a treatment or control group which minimizes bias and confounding. The process by which individuals are asked to volunteer for a study which minimizes bias and confounding. 3.4 points QUESTION 16 A stratified random sample can be used to ensure underrepresented populations are represented in a study. True False 3.4 points QUESTION 17 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. Frequency of Breast Cancer Cases Frequency of Non-Cancer Cases Frequency of Individuals Who Screened Positive 17 5 Frequency of Individuals Who Screened Negative 8 77 A total of 66.67% of individuals who have breast cancer test positive for breast cancer when using a mammogram as the primary diagnostic test for breast cancer. A total of 68% of individuals who have breast cancer test positive for breast cancer when using a mammogram as the primary diagnostic test for breast cancer. A total of 70.59% of individuals who have breast cancer test positive for breast cancer when using a mammogram as the primary diagnostic test for breast cancer. A total of 92.77% of individuals who have breast cancer test positive for breast cancer when using a mammogram as the primary diagnostic test for breast cancer. 3.4 points QUESTION 18 The level of significance is the probability that we reject the null hypothesis (in favor of the alternative) when it is actually true. True False 3.4 points QUESTION 19 Ethnicity is best described as which type of variable? Dichotomous variable Ordinal variable Categorical variable Continuous variable 3.4 points QUESTION 20 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 at a = 0.05. True False 3.4 points QUESTION 21 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. True False 3.4 points QUESTION 22 The level of significance alpha most commonly used are: 0.01, 0.05, 0.1. True False 3.4 points QUESTION 23 Considering the data blow. The median is 120. 100 120 111 115 120 116 125 129 130 True False 3.4 points QUESTION 24 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? 0.67% 6.70% 33.0% 67.0% 3.4 points QUESTION 25 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. True False 3.4 points QUESTION 26 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. We reject H0 at the 5% level because 2.64 is greater than 1.96. We do 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. We fail to reject H0 at the 5% because -2.64 is less than 1.645. We do not have statistically significant evidence to show that there is a difference in the proportions of patients reporting a reduction in symptoms. We fail to reject H0 at the 5% because -2.64 is less than 1.96. We do 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. We fail to reject H0 at the 5% because 2.64 is greater than -1.645. We do 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. 3.4 points QUESTION 27 An r value of .8 indicates a strong positive correlation. True False 3.4 points QUESTION 28 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. 25 27 31 33 26 28 38 41 24 32 35 40 3.4 points QUESTION 29 How many subjects would be needed to ensure that a 95% confidence interval estimate of BMI had a margin of error not exceeding 2 units? 25 27 31 33 26 28 38 41 24 32 35 40 3.4 points QUESTION 30 Based on the data set below , what is the standard deviation? 25 27 31 33 26 28 38 41 24 32 35 40 3.4 points QUESTION 31 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 40 children with chronic bronchitis is studied, and their mean PEF is 279 with a standard deviation of 71. Is there statistical evidence of a lower mean PEF in children with chronic bronchitis? Run the appropriate test at a = 0.05. 3.4 points QUESTION 32 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 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 a = 0.05. Group Number of Children Mean PEF Std Dev PEF Chronic Bronchitis 25 281 68 No Chronic Bronchitis 25 319 74 3.4 points QUESTION 33 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. Preterm Delivery Experimental Drug Standard Drug Placebo Yes 17 23 35 No 83 77 65 Is there a statistically significant difference in the proportions of women delivering preterm among the three treatment groups? Run the test at a 5% level of significance. 3.4 points QUESTION 34 A study is run comparing HDL cholesterol levels between men who exercise regularly and those who do not. The data are shown below. Regular Exercise N Mean Std Dev Yes 35 48.5 12.5 No 120 56.9 11.9 Generate a 95% confidence interval for the difference in mean HDL levels between men who exercise regularly and those who do not. 3.4 points QUESTION 35 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. Standard Treatment Placebo New Treatment 124 134 114 111 143 117 133 148 121 125 142 124 128 150 122 115 160 128 Is there a difference in mean systolic blood pressure among treatments? Run the appropriate test at α = 0.05. 3.4 points QUESTION 36 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 effect of treatment? Run the test at a 5% level of significance. Symptoms Worsened No Effect Symptoms Improved Total Treatment 1 22 14 14 50 Treatment 2 14 15 21 50 Treatment 3 9 12 29 50 3.4 points QUESTION 37 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. Symptoms Worsened No Effect Symptoms Improved Total Treatment 1 22 14 14 50 Treatment 2 14 15 21 50 Treatment 3 9 12 29 50 3.4 points QUESTION 38 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. Treatment Sample Size Mean Time to Relief Sample Variance A 5 33.8 17.7 B 5 27.0 15.5 C 5 50.8 9.7 D 5 39.6 16.8 Complete the following ANOVA Table. Source of Variation SS df MS F Between Groups . Within Groups 3719.48 Total 3.4 points QUESTION 39 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. Subject Initial Weight Weight after 6 Weeks 1 155 157 2 142 145 3 176 180 4 180 175 5 210 209 6 125 126 3.4 points QUESTION 40 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. New Drug: 4 5 3 3 4 2 Standard Drug: 2 3 4 1 2 3 3.4 points QUESTION 41 The following table was presented in an article summarizing a study to compare a new drug to a standard drug and to a placebo. Characteristic* New Drug Standard Drug Placebo p Age, years 45.2 (4.8) 44.9 (5.1) 42.8 (4.3) 0.5746 % Female 51% 55% 57% 0.1635 Annual Income, $000s 59.5 (14.3) 63.8 (16.9) 58.2 (13.6) 0.4635 % with Insurance 87% 65% 82% 0.0352 Disease Stage 0.0261 Stage I 35% 18% 33% Stage II 42% 37% 47% Stage III 23% 51% 20% *Table entries and Mean (Sd. or % Are there any statistically significant differences in the characteristics shown among the treatments? Justify your answer 3.5 points QUESTION 42 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. 3.5 points QUESTION 43 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. 300 140 5600 520 470 700 640 1200 3.5 points QUESTION 44 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. Characteristic Placebo (n = 125) Experimental ( n =125) P Mean (+ Sd. Age 54 + 4.5 53 + 4.9 0.7856 % Female 39% 52% 0.0289 % Less than High School Education 24% 22% 0.0986 % Completing High School 37% 36% % Completing Some College 39% 42% Mean (+ Sd. Systolic Blood Pressure 136 + 13.8 134 + 12.4 0.4736 Mean (+ Sd. Total Cholesterol 214 + 24.9 210 + 23.1 0.8954 % Current Smokers 17% 15% 0.5741 % with Diabetes 8% 3% 0.0438 3.5 points Click Save and Submit to save and submit. Click Save All Answers to save all answers.