Questions and Answers of Fundamentals of Biostatistics

Perform the test in Problem 9.9, and report a p-value?Infectious DiseaseThe distribution of white-blood-cell count is typically positively skewed, and assumptions of normality are usually not
To compare the distribution of white-blood-cell counts of patients on the medical and surgical services in Table 2.13 (p. 36), or in HOSPITAL.DAT, when normality is not assumed, what test can be
Carry out a non-parametric procedure for testing the hypothesis that lengths of stay are comparable in the two hospitals?Health Services AdministrationSuppose we want to compare the length of
Why might a t test not be very useful in this case? Health Services AdministrationSuppose we want to compare the length of hospital stay for patients with the same diagnosis at two different
Answer Problem 9.4 for two samples of size 12 and 15, with a rank sum of 220 in the sample of size 12. Assume there are no ties?Suppose patients are graded on the degree of change in periodontal
Answer Problem 9.4 for two samples of size 7 and 10, with a rank sum of 47 in the sample of size 7. Assume there are no ties?Suppose patients are graded on the degree of change in periodontal status
Suppose there are two samples of size 6 and 7, with a rank sum of 58 in the sample of size 6. Using the Wilcoxon rank-sum test, evaluate the significance of the results, assuming there are no
Implement the procedure in Problem 9.2, and report a p-value?Suppose patients are graded on the degree of change in periodontal status on a 7-point scale, with +3 indicating the greatest improvement,
Obtain a 95% CI for the mean difference in diet record vitamin C intake between the two groups?NutritionThe EPIC-Norfolk study, a study of diet and cancer in Great Britain, was performed to assess
What test can be performed to compare the variances of the two groups?OrthopedicsA study was performed among patients with piriformissyndrome (PS), a pelvic condition that involves malfunction of the
Perform the test in Problem 8.173, and assess whether there is a significant difference between the variances at the 5% level?OrthopedicsA study was performed among patients with piriformissyndrome
What test can be performed to compare the means of the two groups?OrthopedicsA study was performed among patients with piriformissyndrome (PS), a pelvic condition that involves malfunction of the
What nonparametric test can be used to determine whether a significant change in periodontal status has occurred over time? Suppose patients are graded on the degree of change in periodontal
Perform the test in Problem 8.175, and report a two-sided p-value?OrthopedicsA study was performed among patients with piriformissyndrome (PS), a pelvic condition that involves malfunction of the
Assess the impact of the program statistically (use a two-sided test)?DentistryIn a study, 28 adults with mild periodontal disease are assessed before and 6 months after implementation of a
Perform the test in Problem 8.170, and report a p-value (two-tailed)?NutritionThe EPIC-Norfolk study, a study of diet and cancer in Great Britain, was performed to assess the relationship between
What test can be performed to compare the mean diet record vitamin C intake between the two groups?NutritionThe EPIC-Norfolk study, a study of diet and cancer in Great Britain, was performed to
Perform the test in Problem 8.168, and identify whether there is a significant difference between the two variances (i.e., is p < .05 or p > .05?).NutritionThe EPIC-Norfolk study, a study of
What test can be used to compare the standard deviation of diet record vitamin C intake between current smokers vs. nonsmokers?NutritionThe EPIC-Norfolk study, a study of diet and cancer in Great
Perform the test in Problem 8.166, and report a p-value (two-tailed)?Another way to compare the E-treated eyes vs. the C-treated eyes is to look at the percentage of subjects who have less pain in
If the E and C treatments are comparable, what test can we use to compare the percentage of subjects who have less pain with the E eye vs. the C eye? Another way to compare the E-treated eyes
Perform this test, and report a p-value (two-tailed)?OphthalmologyThe following data are from a study on Botox injections. Patients received a high-dose injection in one eye (experimental treatment =
What test can be used to make this comparison?OphthalmologyThe following data are from a study on Botox injections. Patients received a high-dose injection in one eye (experimental treatment =
The above study had no control group. Assuming that the same standard deviation of change would occur among controls and the mean change among controls = 0, how many participants would be necessary
What minimum sample size would be needed to detect a mean change of 5 units with 80% power if a two-sided test is used with α = .05?NeurologyIn a 5-year follow-up of bilateral stimulation of the
How much power does this study have to detect a mean difference of 5 units in the symptom scale if a two-sided test is used with α = .05? NeurologyIn a 5-year follow-up of bilateral stimulation
Suppose this study is a pilot study for a larger study. The investigators want to determine the sample size in the larger study so that(i) Power will be 90%(ii) A two-sided test is used with a =
Suppose that the mean in group 1 = 15.4 and the mean in group 2 = 12.6. Based on your answer to Problem 8.158 test whether the means in the two groups are significantly different, and report a
Group 1 has a sample sd of 10.0 (n = 8) while group 2 has a sample sd = 8 ( n = 15). Test whether the variances in the two groups are significantly different at the 5% level?GeneralSuppose we have
Provide a 95% CI for the difference in mean baseline heart rate between starting an exercise program (2000) and after 10 years of regular exercise (2010)?The subject also recorded his heart rate at
Interpret the results of the test in Problem 8.155?The subject also recorded his heart rate at baseline and 5 minutes after starting treadmill exercise (at a speed of 2.5 mph) in 2000. The data are
Implement a test to compare the baseline heart rate initially (2000) and after 10 years of exercise (2010), and report a two-sided p-value?The subject also recorded his heart rate at baseline and 5
Provide a 95% CI for the mean change in heart rate after using the treadmill for 5 minutes. The subject also recorded his heart rate at baseline and 5 minutes after starting treadmill exercise (at a
Suppose we wanted a 99% CI. Would this interval be longer, shorter, or the same size as the 95% CI in Problem 8.152? (Do not actually compute the interval.)DiabetesThe insulin pump is a device that
Provide a 95% CI for the mean difference in HgbA1c before minus the mean HgbA1c after use of the insulin pump?DiabetesThe insulin pump is a device that delivers insulin to a diabetic patient at
Perform the test in Problem 8.150, and report a twotailed p-value?DiabetesThe insulin pump is a device that delivers insulin to a diabetic patient at regular intervals. It presumably regulates
What test can be used to compare the mean HgbA1c 1 year before vs. mean HgbA1c 1 year after use of the insulin pump?DiabetesThe insulin pump is a device that delivers insulin to a diabetic patient at
Suppose that 100 Caucasian and 150 African American subjects are actually enrolled in the study. How much power would the study have to detect a 5-mg/dL mean difference using a two-sided test with
Suppose a new study is conducted in which there will be n1Caucasian subjects and n2African American subjects, where n2= 2n1. How large should n1and n2 be in order for the new study to have 90%
Provide a 95% CI for the difference between the means?Cardiovascular DiseaseA study of genetic factors related to coronary heart disease (CHD) was performed as a substudy within the ARIC Study [20].
What is the standard error of the mean for each group?Cardiovascular DiseaseA study of genetic factors related to coronary heart disease (CHD) was performed as a substudy within the ARIC Study [20].
Provide a 95% CI for the difference in mean adult height between women in the first and fourth quartiles?PediatricsA study was conducted to assess the association between climate conditions in
Perform the test in problem 8.143, and report a p-value (two-tailed). Assume that the underlying variances in Q1 and Q4 are the same?PediatricsA study was conducted to assess the association between
What test can be performed to compare the mean adult height between the first (Q1) and the fourth (Q4) quartiles? (Assume that the underlying variances of adult height in Q1 and Q4 are the
What is the standard deviation of adult height for the women in the first quartile group (group Q1)?PediatricsA study was conducted to assess the association between climate conditions in infancy and
Do boys with better glycemic control have different growth patterns in weight than boys with poorer glycemic control?
How many participants should be enrolled in each group in a future study, if(a) The true mean difference in age at menarche between girls with low- and high-childhood- SES is 0.5 year,(b) Standard
Perform the test in Problem 8.136, and report a two tailed p-value?CancerAge at menarche (onset of menstrual periods) is an important risk factor for breast cancer and possibly ovarian cancer. In
What test can be used to compare the mean of the two groups?CancerAge at menarche (onset of menstrual periods) is an important risk factor for breast cancer and possibly ovarian cancer. In general,
Perform the test in Problem 8.134, and report a p-value (two-tailed)?HematologyInsulin-like growth factor 1 (IGF-1) is a hormone that plays an important role in childhood growth and may be associated
Assuming that the distribution of IGF-1 is approximately normal, what test can be used to compare the mean IGF-1 obtained from the two sources? HematologyInsulin-like growth factor 1 (IGF-1) is
Suppose the true mean increase in BMI among heavy-smoking women 6 years after quitting is 3.0 kg/m2with a standard deviation of 2.5 kg/m2. The comparable true mean increase in BMI among never-smoking
Implement the test in Problem 8.131, and report a two-tailed p-value?One issue is that there has been a secular change in weight in society. For this purpose, a control group of 50- to 54-year-old
What test can be used to assess whether the mean change in BMI over 6 years is different between women who quit smoking and women who have never smoked?One issue is that there has been a secular
Implement the test in Problem 8.129, and report a two-tailed p-value?Health PromotionCigarette smoking has important health consequences and is positively associated with heart and lung diseases.
What test can be used to assess whether the mean BMI changed significantly among heavy-smoking women 6 years after quitting smoking? Health PromotionCigarette smoking has important health
Implement the test in Problem 8.127, and report a two-tailed p-value?Health PromotionA study looked at the influence of retirement on the level of physical activity among people ages 45ˆ’64
What test can be used to assess whether the underlying mean change score differs for retired women vs. working women?Health PromotionA study looked at the influence of retirement on the level of
Suppose a similar study is planned among women who use exogenous hormones. How many participants need to be enrolled if the mean change in log10 (plasma estradiol) is −0.08, the standard deviation
Suppose we want to estimate the number of participants needed in the main study so that there is a 90% chance of finding a significant difference between active and placebo eyes using a two-sided
Suppose 60 participants are enrolled in the main study. How much power would the study have to detect a 0.5-unit mean difference if a two-sided test is used with a significance level of
In a substudy, participants will be subdivided into two equal groups according to the severity of previous allergy symptoms (n = 30 each), and the effectiveness of the eye drop (vs. placebo) will be
What test can be used to assess if there is a change in mean LVM over four years? Cardiovascular DiseaseLeft ventricular mass (LVM) is an important risk factor for subsequent cardiovascular
Implement the test in Problem 8.106, and provide a two-tailed p-value?Cardiovascular DiseaseLeft ventricular mass (LVM) is an important risk factor for subsequent cardiovascular disease. A study is
Provide a 95% Cl for the change in LVM over 4 years based on the data in Table 8.27?Cardiovascular DiseaseLeft ventricular mass (LVM) is an important risk factor for subsequent cardiovascular
Since this was a pilot study, the main question of interest is how many subjects would be needed to detect a mean increase of 10 g in LVM over four years using a two-sided test with a = 0.05 and
Provide a 95% CI for the mean pod weight in each group?MicrobiologyA study sought to demonstrate that soy beans inoculated with nitrogen-fixing bacteria yield more and grow adequately without the use
Suppose there is some overlap between the 95% CIs in Problem 8.110. Does this necessarily imply there is no significant difference between the mean pod weights for the two groups? Why or why
What test can be used to compare the mean pod weight between the two groups?MicrobiologyA study sought to demonstrate that soy beans inoculated with nitrogen-fixing bacteria yield more and grow
Perform the test in Problem 8.112, and report a p-value (two-tailed)?MicrobiologyA study sought to demonstrate that soy beans inoculated with nitrogen-fixing bacteria yield more and grow adequately
Provide a 95% CI for the difference in mean pod weight between the two groups?MicrobiologyA study sought to demonstrate that soy beans inoculated with nitrogen-fixing bacteria yield more and grow
One hypothesis is that analgesic abusers would have different serum-creatinine profiles at baseline. Using the data from the baseline visit, can you address this question?
A major hypothesis of the study is that women with high phenacetin intake would show a greater change in serum-creatinine level compared with women with low phenacetin intake. Can you assess this
Suppose we want to compute a two-sided p-value for this comparison. Without doing any further calculation, which statement(s) must be false?(1) p = .01(2) p = .04(3) p = .07(4) p = .20(The actual
Suppose we assume that the standard deviation of change in blood pressure is the same in each group and is known without error. Compute the exact p-value from the information provided?HypertensionA
Suppose we want to compute a two-sided 95% CI for the true mean change in the fruits-and-vegetables group minus the true mean change in the control group, which we represent by (c1, c2). Without
Making the same assumption as in Problem 8.118, compute the 95% CI from the information provided?HypertensionA study was recently reported comparing the effects of different dietary patterns on blood
What test can be used to assess mean changes in weight in the intervention group? DiabetesThe Diabetes Prevention Study was a randomized study conducted in Finland in which middle-aged
Perform the test in Problem 8.121, and report a two-tailed p-value?DiabetesThe Diabetes Prevention Study was a randomized study conducted in Finland in which middle-aged participants (mean age 55
What test can be used to compare mean change in weight between the intervention and control groups? (Note: F255,249,.975= 1.281.)DiabetesThe Diabetes Prevention Study was a randomized study conducted
Perform the test in Problem 8.123, and report a two tailed p-value?DiabetesThe Diabetes Prevention Study was a randomized study conducted in Finland in which middle-aged participants (mean age 55
What are the standard deviation and standard error of the mean for the change score for retired women? Health PromotionA study looked at the influence of retirement on the level of physical
Construct a two-sided 90% CI for the mean change score for retired women. What does it mean?Health PromotionA study looked at the influence of retirement on the level of physical activity among
Provide a 95% CI for the change in mean log10 (plasma estradiol)?EndocrinologyA study was performed to determine the effect of introducing a low-fat diet on hormone levels of 73 postmenopausal women
Implement the test in Problem 8.99, and report a p-value?EndocrinologyA study was performed to determine the effect of introducing a low-fat diet on hormone levels of 73 postmenopausal women not
What test can be performed to assess the effects of adopting a low-fat diet on mean plasma-estradiol levels? EndocrinologyA study was performed to determine the effect of introducing a low-fat
How much power did the study have for detecting a significant difference between groups (using a two-sided test with a 5% level of significance) if the true effect of the SMI intervention is to
Implement the test in Problem 8.96, and report a two-tailed p-value?The results for the control group (n = 320) at the end of the study were as follows:Mean (change) = −4.77 mm Hg,sd (change) =
What test can be used to compare mean blood pressure change between the two groups? The results for the control group (n = 320) at the end of the study were as follows:Mean (change) = −4.77 mm
Implement the test in Problem 8.94, and report a p-value?HypertensionA study was performed comparing different nonpharmacologic treatments for people with high-normal diastolic blood pressure (DBP)
What test can be used to assess whether mean blood pressure has changed significantly in the SMI group?HypertensionA study was performed comparing different nonpharmacologic treatments for people
Implement the test in Problem 8.92, and report a two-tailed p-value?OphthalmologyA study compared mean electroretinogram (ERG) amplitude of patients with different genetic types of retinitis
What test can be used to compare the mean ln (ERG amplitude) between patients with dominant vs. recessive RP?OphthalmologyA study compared mean electroretinogram (ERG) amplitude of patients with
Implement the test in Problem 8.90, and report a p- value (two-tailed)?OphthalmologyA study compared mean electroretinogram (ERG) amplitude of patients with different genetic types of retinitis
What test can be used to compare the variance of ln (ERG amplitude) between patients with dominant vs. recessive RP? OphthalmologyA study compared mean electroretinogram (ERG) amplitude of
What is the standard error of ln(ERG amplitude) among patients with dominant RP? How does it differ from the standard deviation in the table? OphthalmologyA study compared mean electroretinogram
Refer to Data Set FEV.DAT atwww.cengagebrain.com. Assess whether there are any outliers in FEV for the following groups: 5- to 9-year-old boys, 5- to 9-year-old girls, 10- to 14-year-old boys, 10- to
Based on your answers to Problems 8.85 and 8.86, compare mean full-scale IQ between the exposed and the control groups, after the exclusion of outliers?Environmental Health, PediatricsRefer to Figure
Assess whether there are any outliers for full-scale IQ in the exposed group?Environmental Health, PediatricsRefer to Figure 8.12 (p. 313) and Table 8.7 (p. 305).Figure 8.12: Stem-and-leaf and box
Assess whether there are any outliers for full-scale IQ in the control group?Environmental Health, PediatricsRefer to Figure 8.12 (p. 313) and Table 8.7 (p. 305).Figure 8.12: Stem-and-leaf and box

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