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biostatistics
Basic Biostatistics Statistics For Public Health Practice 2nd Edition B.Burt Gerstman - Solutions
Select the best response: We have pretest and posttest samples.Which t procedure should we use?(a) a one-sample t procedure(b) a paired t procedure(c) an independent t procedure
Identify two graphical methods that can be used to compare quantitative data from two independent groups.
This symbol represents the sample mean of group i.
This symbol represents the sample standard deviation of group i.
This symbol represents the sample variance of group i.
This symbol represents the population mean of group i.
This symbol represents the population standard deviation of group i.
This is the point estimator of μ1− μ2.
The statistic quantifies the precision of the sample mean difference as an estimate of the population mean difference.
Select the best response: The degrees of freedom for independent t procedures that do not assume equal variance may be based on a conservative method or a method attributed to:(a) Student(b) Fisher(c) Welch
Fill in the blank: The conservative estimate for the degrees of freedom for the unequal variance t procedures is the _______ of (n1−1) or (n2− 1).
Select the best response: Independent t procedures (unequal variance option) require independent samples and(a) equal variances in the population.(b) Normal populations.(c) Normal populations or a large enough sample to compensate for non-Normality through the central limit theorem.
Homoscedasticity means the population(a) has equal variances.(b) has equal means.(c) is Normal.
List the three factors that govern the sample size requirements for estimating population mean differences.
Select the best response: Maximum power of a statistical test is achieved when the sample size for group 1 is _______ the sample size for group 2.(a) greater than(b) less than(c) equal to
List the four factors that determine the sample size requirements of an independent t test.
List the four factors that govern the power of an independent t test.Exercises 12.11 Testing a test kit. Would you use a one-sample, paired-sample, or independent-sample t procedure in the following situations?(a) A lab technician obtains a specimen of known concentration from a reference lab.
Lactation and bone loss. A study compares changes in bone density in 22 women who are neither pregnant nor breastfeeding to that of 47 comparably aged women who are breastfeeding. Table 12.13 lists percent changes in bone mineral content in the spines of these women.(a) Compare these groups with
Risk-taking behavior in boys and girls. A questionnaire measures an index of risk-taking behavior in respondents. Scores are standardized so that 100 represents the population average. The questionnaire is applied to a sample of teenage boy and girls. Data are:i Explore group differences with
Scrapie treatment, delay of symptoms. Scrapie is a prion disease similar in pathology to bovine spongiform encephalopathy (mad cow disease) and new variant Creutzfeldt-Jakob disease. In a study of 20 scrapie-infected hamsters, 10 were treated with a substance known as IDX and 10 were left
Scrapie treatment, delay of death. Refer to the previous exercise.The mean survival time in the IDX-treated group was 116 days (SE1= 5.6). The mean survival time in the control group was
(SE2 =1.9). Test H0: μ1= μ2.
Cytomegalovirus and coronary stenosis. Coronary stenosis(narrowing of the artery supply to the heart muscle) is a direct cause of heart disease. A theory suggests that chronic cytomegalovirus(CMV) infection narrows coronary vessels and leads to coronary heart disease. To test this theory, 75
Bone density in newborns. In a study of maternal cigarette smoking and bone density in newborns, 77 infants of mothers who smoked had a mean bone mineral content of 0.098 g/cm3 (s1 = 0.026 g/cm3).The 161 infants whose mothers did not smoke had a mean bone mineral content of 0.095 g/cm3(s2= 0.025
Hemodialysis and anxiety. Severe anxiety often accompanies patients who must undergo chronic hemodialysis. A study was undertaken to determine the effects of a set of progressive relaxation exercises on anxiety in hemodialysis patients. The treatment group consisted of 38 subjects who were shown a
Efficacy of echinacea, severity of symptoms. A randomized, doubleblind, placebo-controlled study evaluated the effects of the herbal remedy Echinacea purpurea in treating upper respiratory tract infections in 2- to 11-year-olds. Each time a child had an upper respiratory tract infection, treatment
Efficacy of echinacea, duration of symptoms. The study introduced in the prior exercise also compared duration of peak symptoms in the treatment and control group. The treatment group (n1 = 337) had a mean duration of 1.60 days (standard deviation 0.98 days). The control group (n2 = 370) had a mean
Calcium supplementation and blood pressure, exploration. Table 12.3 contains data from a randomized, double-blind, placebocontrolled trial that examined the effects of calcium supplementation on blood pressure in normotensive men. After establishing a baseline blood pressure measurement, subjects
Calcium supplementation and blood pressure, hypothesis test.(a) Calculate summary statistics for the groups described in Exercise 12.21.(b) Test the mean difference for significance.
Delay in discharge. Delays in discharges from intermediate healthcare facilities create unnecessary risks and expenses for patients and their families. Discharge delays (in days) from two healthcare facilities are shown in the following table. Assume that these data represent SRSs from their
Time spent standing or walking. A study was undertaken to compare daily activity levels in lean (group 1) and obese (group 2) study subjects. Sensors monitored the type and amount of routine daily activities such as walking, sitting, and lying down in each subject.Data are shown in Table 12.15.
Time spent standing or walking. This exercise continues our analysis of data from the study by Levine and coworkers (2005)introduced in Exercise 12.24. We now wish to test whether lean and obese differ in the amount they sit each day (column 3). Data appear in Table 12.15 and can be downloaded from
Birth weight, exploration. Table 13.3 lists birth weights of infants based on the smoking status of mothers.(a) Outline this study’s design using a sketch of the type presented in Section 2.2(see Figure 2.1) to depict this study’s design.(Comment: In contrast to the pets and stress illustrative
Laboratory experiment, exploration. The ubiquity of junk food may contribute to the high prevalence of obesity in western societies.Table
lists data from a study in which 15 lab mice were randomly assigned to one of three groups: group 1 received a standard diet, group 2 received a diet of junk food, and group 3 received an organic diet. The response variable is weight gains(grams) over a 1-month period.(a) Outline the design of this
Smoking and birth weight, ANOVA. Exercise 13.1 presented data on birth weights of infants based on the smoking status of mothers.Table 13.3 lists the data. Descriptive statistics are shown in Table 13.10. Conduct an ANOVA on these data. Show all hypothesistesting steps.
Laboratory experiment, ANOVA. Recall the laboratory experiment described in Exercise 13.2. The response variable is weight gains (in grams). There are three groups of lab animals, each with five test animals. Data are shown in Table 13.4. Complete a one-way analysis of variance for this problem.
Smoking and birth weight, post hoc comparisons. The ANOVA in Exercises 13.3 found that birth weight of four groups of infants differed significantly according to the smoking status of mothers (P= 0.042). Table 13.3 lists the data for the analysis. Data are also available online in the file
Laboratory experiment, post hoc comparisons. Exercises 13.2 and 13.4 considered weight gain in three groups of lab mice. Table 13.4 lists data for the problem. Results from the ANOVA were significant(P = 0.015). Complete post hoc comparisons of the groups using the Bonferroni method.
Smoking and birth weight, Kruskal–Wallis test. Exercises 13.1, 13.3, and 13.5 considered birth weight in four groups of mothers.Table 13.3 lists the data. Data are also stored online in the file SMOK_BW.SAV. The ANOVA test found significant evidence against H0(P = 0.042). Now apply a
Laboratory experiment, Kruskal–Wallis test. Recall the experiment concerning weight gain in lab animals fed different diets (Exercises 15.2, 15.4, and 15.6). Table 13.4 lists the data. Conduct a Kruskal–Wallis test for these data, showing all hypothesis-testing steps.
What does ANOVA stand for?
Select the best response: This chapter compares the results from two or more groups when the response variable is ______.(a) quantitative(b) ordinal(c) categorical
List two graphical techniques that can be used to compare the shapes, locations, and spreads of a data from two or more independent groups.
Identify two indicators of spread that are visible on boxplots.
Fill in the blank: When reporting group summary statistics for quantitative response variables, you should always report group sample sizes, means, and ______.
Select the best response: The Problem of Multiple Comparisons occurs when you identify too many ______ differences as a result of making too many comparisons.(a) true (b) systematic (c) random
Completing multiple hypothesis tests undermines the intention of restricting the number of type I errors advertised by the nominal ______ level.(a) α(b) β(c) power
How many different possible pair-wise comparisons are there in testing 10 groups?
In testing 45 true null hypotheses using an α threshold of 0.05, what is the probability that you will retain all 45 true null hypothesis?What is the probability that you will reject at least one (true) null hypothesis?
In testing 45 true null hypotheses using an α threshold of 0.01, what is the probability that you will retain all 45 true null hypothesis?What is the probability that you will reject at least one (true) null hypothesis?
Fill in the blank: The null hypothesis in testing the means from four groups with one-way ANOVA is ______.
Fill in the blank: The alternative hypothesis in testing the means from four groups with one-way ANOVA is ______.
Select the best response: The variance is equal to the ______ standard deviation.(a) logarithm(b) square root(c) squared
Select the best response: The variance is a measure of ______.(a) shape(b) spread (c) location
Select the best response: Evidence of nonrandom differences in group means occurs when the variance between groups is ______ the variance within groups.(a) much greater than(b) much less than(c) about equal to
Select the best response: The variance within groups is estimated by the(a) mean difference(b) mean square between(c) mean square within
Select the best response: The mean of all the observations combined in the data set is called the(a) mean difference(b) grand mean(c) group mean
Select the best response: This statistic quantifies the variability of the group means around the grand mean.(a) mean difference(b) mean square between(c) mean square within
The means square within (MSW) is equal to ______ divided by dfW.
The F-statistic is equal to the mean square between (MSB) divided by the ______.
A large F-statistics indicates a large signal to ______ ratio, suggesting that the observed difference is not random.
F-probability density function curves have long right ______.
Select the best response: One-way ANOVA when restricted to the comparison of means from two groups is equivalent to a(n) ______ test.(a) z(b) unequal variance independent t-test(c) equal variance independent t-test
One procedure for making post hoc comparisons following ANOVA procedure is referred to as the LSD method. What does LSD stand for?
True or false? Post hoc comparisons made with LSD procedures are usually reserved for unplanned comparisons.
Select the best response: A Bonferroni-adjusted P-value compensates ______.(a) invalid data(b) the problem of multiple comparisons(c) violations in the conditions for the ANOVA
Complete this sentence: The Bonferroni adjustment for multiple comparisons avoids more type I errors than the LSD method, but makes more ______ errors.
List the three statistical conditions required for ANOVA.
Change one word in this sentence to make it correct: The conditions required for valid ANOVA are the same as those for an unequal variance independent t-test.
What does homoscedastic mean?
List three methods to assess whether population variances are equal.
Write the null hypothesis addressed by Levene’s test of three groups.
List options for dealing with heteroscedasticity.
What makes a hypothesis test “robustness”?
What is the name of the nonparametric test that is functionally equivalent to one-way ANOVA?
State the null hypothesis tested by the Kruskal–Wallis procedure.Exercise 13.9 Antipyretics trial. A trial evaluated the fever-reducing effects of three substances. Study subjects were adults seen in an emergency room with diagnoses of flu with body temperatures between 100.0 and 100.9°F. The
lists the data.(a) Explore these data with side-by-side boxplots. Discuss your findings.(b) Calculate the mean and standard deviation of each group.TABLE
Data for Exercise 13.9. Decreases in body temperatures (degrees Fahrenheit).Data are also stored online in the file ANTIPYRE.SAV.(c) Complete an ANOVA for the problem. What do you conclude?(d) Conduct post hoc comparisons with the LSD method. Which groups differ significantly at α = 0.05?
Melanoma treatment. An experiment evaluated the use of genetically engineered white blood cells in the treatment of patients with melanoma.y Patients were divided into three cohorts. Patient cohort 1 received genetically engineered lymphocytes that were cultured ex vivo for 19 days. Cohort 2
Bicycle helmet use. Table 14.5 lists data from a cross-sectional survey of bicycle safety. The explanatory variable is a measure of neighborhood socioeconomic status (variable P_RFM). The response variable is “percent of bicycle riders wearing a helmet” (P_HELM).(a) Construct a scatterplot of
Mental health care. This exercise uses data from a historical study on mental health service utilization.j Fourteen Massachusetts counties are considered. The explanatory variable is the reciprocal of the distance to the nearest mental healthcare center (miles−1, REC_DIST). The response variable
Fill in the blank: In regression problems, the explanatory variable is represented by X and the response variable is represented by ______.
Fill in the blank: In regression problems, the explanatory variable is referred to as the independent variable and the response variable is referred to as the ______ variable.
Select the best response: The explanatory variable in a linear correlation and regression problem is recorded on this measurement scale.(a) categorical(b) ordinal(c) quantitative
Select the better response: The response variable in a linear correlation and regression problem is recorded on this measurement scale.(a) categorical(b) ordinal(c) quantitative
Why are scatterplots necessary when investigating the relationship between quantitative variables?
What four elements do we look for when viewing a scatterplot?
Why is it difficult to judge the strength of an association by eye when viewing a scatterplot?
What symbol represents Pearson’e correlation coefficient statistic?
What symbol represents Pearson’s correlation coefficient parameter?
Fill in the blanks: r is always greater than or equal to ______ and less than or equal to ______
Which r indicates a stronger association, −0.56 or +0.48?
When there is no linear correction between X and Y, ρ = ______.
Select the best response: Perfect negative association is present when r = ______.(a) 1(b) 0(c) −1
Select the best response: According to our benchmarks, a correlation is considered strong when(a) r > 0.3(b) r > 0.7(c) |r| > 0.7
Complete this statement: H0: ρ = ______.
Fill in the blanks: The least squares regression line is given by.
In the above statement, what does represent?
What symbol is used to denote the intercept of a regression line?
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