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biostatistics
Basic Biostatistics Statistics For Public Health Practice 2nd Edition B.Burt Gerstman - Solutions
What represents the predicted change in Y unit X?
What symbol represents the slope estimate?
What symbol represents the slope parameter?
What is wrong with this statement? “A 95% confidence interval for b is −0.91 to −0.42.”
What is the distance of a data point from the regression line called?
Besides linearity, what conditions are needed to infer population slope β?
Besides linearity, what conditions are needed to infer population correlation coefficient ρ?
Complete this statement: (residual i) = (observed Y value of i) −______.
In symbols, residuali= yi− ______.
What is wrong with this statement? “H0: r = 0.”
Fix this statement: “Ha: β = 0”. (Four fixes are possible.)Exercises 14.3 Bicycle helmet use, n = 12. Exercise 14.1 introduced data for a cross-sectional survey of bicycle helmet use in Northern California.Table 14.5 lists the data. Exercise 14.1(a) revealed that observation 13 (Los Arboles)
Mental health care. Exercise 14.2 introduced historical data in which the explanatory variable was the reciprocal of the distance to the nearest healthcare facility (miles−1, variable name REC_DIST) and the response variable was the percent of patients cared for at home(variable name PHOME2).
Anscombe’s quartet. “Graphs are essential to good statistical analysis,” so starts a 1973 article by Anscombe.q This article demonstrates why it is important to look at the data before analyzing it numerically. Table
contains four different data sets. Each of the data sets produces these identical numerical results:Figure
shows scatterplots for each of the data sets. Consider the relevance of the numerical statistics in light of the scatterplots.Would you use correlation or regression to analyze any of these data sets? Explain your reasoning in each instance.
Domestic water and dental cavities. Table
contains data from a historically important study of water fluoridation and dental caries in 21 North American cities.(a) Construct a scatterplot of FLUORIDE and CARIES. Discuss the plot.Are there any outliers? Is the relationship linear? If the relationship is not linear, what type of relation is
Domestic water and dental cavities, range restriction. Another way to look at the data presented in Exercise 14.6 is to restrict the analysis to a range that can be described with a straight line. This is called a range restriction.(a) Use the scatterplot you drew in Exercise 14.6(a) to determine
Correlation matrix. Statistical packages can easily calculate correlation coefficients for multiple pairings of variables. Results are often reported in the form of a correlation matrix. Figure 14.18 displays the correlation matrix for data from a study of geographic variation in cancer rates.r The
True or false? Identify which of these statements are true and which are false.(a) Correlation coefficient r quantifies the relationship between quantitative variables X and Y.(b) Correlation coefficient r quantifies the linear relation between quantitative variables X and Y.(c) The closer r is to
Memory of food intake. Retrospective studies of diet and health often rely on recall of distant dietary histories. The validity and reliability of such information is often suspected. An epidemiologic study asked middle-aged adults (median age 50) to recall food intake at ages 6, 18, and 30 years.
is always on the least squares regression line. The least square regression line will always go through the point . Prove that when (Hint: Recall that ; replace a in the first equation for the equivalent provided in the second equation and voilà!)
Historically important coronary heart disease study. Following World War II, many northern European countries experienced notable increases in what was then called degenerative heart disease and is now called coronary heart disease. In 1953, an investigator by the name of Ancel Keys reported the
Nonexercise activity thermogenesis (NEAT). We routinely burn calories through the nonexercise activities of daily life. In this exercise, we will use the acronym NEAT to refer to “nonexercise activity thermogenesis.” NEAT includes such activities of daily living, fidgeting, maintenance of
Neuroimaging social rejection. A study examined the correlates of social exclusion (a social stressor) by neuroimaging an activity in the anterior cingulate cortex (a part of the brain whose activity is associated with physical pain). Study subjects filled out a questionnaire that assessed the
Gorilla ebola. An ebola virus outbreak in gorillas in the Congo from 2002 to 2003 killed 91 gorillas in 7 ranges. This table list ONSET date relative to the initiation of the outbreak and the number of home ranges separating the gorilla band from the initially infected band (DISTANCE):DISTANCE
Sodium and systolic blood pressure. Data from 10 individuals in renal failure with high blood pressure are shown in the following table. The variable SODIUM represents salt consumption (in milligrams) and the variable BP represents systolic blood pressure (in mmHg).(a) Demonstrate the relationship
The relation between FEV and SEX in the illustrative data set.Download the illustrative data set (FEV.*) used in this chapter. See Table
for a codebook of variables. Examine the relationship between FEV and SEX. Then, examine the relationship between FEV and SEX while adjusting for AGE. Did AGE confound the relationship?
Cognitive function in centenarians. A geriatric researcher looked at the effect of AGE (years), EDUCATION level (years of schooling), and SEX (0 = female, 1 = male) on cognitive function in 162 centenarians(fictitious data). Cognitive function was measured using standardized psychometric and mental
Value, variable, observation. In Table 1.2, what is the value of the LUNGCA variable for the 7th observation? What is the value of the COUNTRY variable for the 11th observation?
Value, variable, observation (cont.). What is the value of the CIG1930 variable for observation 3 in Table 1.2?
Value, variable, observation (cont.). In the form depicted in Figure 1.1, what does VAR3 measure?
Value, variable, observation (cont.). In Table 1.1, what is the value of VAR4 for observation 3?
What types of activities other than “calculations” and “math” are associated with the practice of statistics?
Select the best response: Data in a column in a data table corresponds to a(n):(a) observation(b) variable(c) value
Select the best response: Data in a row in a data table corresponds to a(n):(a) observation(b) variable(c) value
List the three main measurement scales addressed in this chapter.
What type of measurement assigns a name to each observation?
What type of measurement is based on categories that can be put in rank order?
What type of measurement assigns a numerical value that permits for meaningful mathematical operations for each observation?
What does GIGO stand for?
Provide synonyms for categorical data.
Provide synonyms for quantitative data.
Differentiate between imprecision and bias.
How is imprecision quantified?
Duration of hospitalization. Table
contains data from an investigation that studied antibiotic use in hospitals.(a) Classify each variable as quantitative, ordinal, or categorical.(b) What is the value of the DUR variable for observation 4?(c) What is the value of the AGE variable for observation 24?
Clustering of adverse events. An investigation was prompted when the U.S. Food and Drug Administration received a report of an increased frequency of an adverse drug-related event after a hospital switched from the innovator company’s product to a generic product.To address this issue, a team of
lists data for the first 25 patients in the study.a) Classify each variable in the table as either quantitative, ordinal, or categorical.(b) What is the value of the AGE variable for observation 4?(c) What is the value of the DIAG (diagnosis) variable for observation 2?
Dietary histories. Prospective studies on nutrition often require subjects to keep detailed daily dietary logs. In contrast, retrospective studies often rely on recall. Which method—dietary logs or retrospective recall—do you believe is more likely to achieve accurate results? Explain your
Variable types. Classify each of the measurements listed here as quantitative, ordinal, or categorical.(a) Response to treatment coded as 1= no response, 2 = minor improvement, 3 = major improvement, 4 = complete recovery(b) Annual income (pretax dollars)(c) Body temperature (degrees Celsius)(d)
Variable types 2. Here is more practice in classifying variables as quantitative, ordinal, or categorical.(a) White blood cells per deciliter of whole blood(b) Leukemia rates in geographic regions (cases per 100,000 people)(c) Presence of type II diabetes mellitus (yes or no)(d) Body weight (kg)(e)
Rating hospital services. A source ranks hospitals based on each of the following items. (The unit of observation in this study is“hospital.”) Identify the measurement scale of each item as quantitative, ordinal, or categorical.(a) Percentage of patients who survive a given surgical
Age recorded on different measurement scales. We often have a choice of whether to record a given variable on either a quantitative or a categorical scale. How does one measure age quantitatively?Provide an example by which age can be measured categorically.
Physical activity in elementary school children. You are preparing to study physical activity levels in elementary school students.Describe two quantitative variables and two categorical variables that you might wish to measure.
Binge drinking. “Binge alcohol use” is often defined as drinking five or more alcoholic drinks on the same occasion at least one time in the past 30 days. The following table lists data from the National Survey on Drug Use and Health based on a representative sample of the U.S. population of
8.8 18−25 41.6 41.8 26 and above 21.0 22.1 Data from National Data Book, 2012 Statistical Abstract, United States Census Bureau, Table 207.Retrieved from www.census.gov/compendia/statab/2012edition.html. Accessed February 18, 2013.Classify the measurement scale of each of the variables in this
Assessing two sets of measurements. Two sets of measurements are given in the following list. Which set of measurements is more precise? Can you determine which is less biased? Explain your reasoning.
Sample and population. For the scenarios presented here, identify the source population and sample as specifically as possible. If information is insufficient, do your best to provide a reasonable description of the population and sample and then suggest additional“person, place, and time
A survey of rheumatoid arthritis patients. A survey mailed questionnaires to 486 patients with rheumatoid arthritis. Responses were received from 334 patients, corresponding to a response rate of 69%. Nonresponders were traced and approached for a telephone interview. Two percent of the responders
California counties. As a pilot investigation for a survey of California county health departments, you want to select four counties at random from the list of counties in Table 2.1. Use the table of random digits (Table A) starting in row 33 to select your simple random sample.
Explanatory variable and response variable. Identify the explanatory variable and response variable in each of the studies described here.(a) A study of cell phone use and primary brain cancer suggested that cell phone use was not associated with an elevated risk of brain cancer.k(b) Records of
Experimental or nonexperimental? Determine whether each of the studies described in Exercise 2.4 are experimental or nonexperimental. Explain your reasoning in each instance.
MRFIT. The MRFIT study discussed in an earlier illustrative example studied 12,866 high-risk men between 35 and 57 years of age. Approximately half the study subjects were randomly assigned to a special care group; the other half received their usual source of care. Death from coronary disease was
Five-City Project. The Stanford Five-City Project is a comprehensive community health education study of five moderately sized Northern California towns. Multiple-risk factor intervention strategies were randomly applied to two of the communities. The other three cities served as controls.p Outline
MRFIT. The MRFIT field trial discussed as an illustrative example studied 12,866 high-risk men between 35 and 57 years of age. Use Table A starting in row 03 to identify the first two members of the treatment group.
Five-City Project. The Stanford Five-City Project (Exercise 2.7)randomized cities to either a treatment or a control group. Number the cities 1 through 5. Use Table A starting in line 17 to randomly select the two treatment cities.
Controlled-release morphine in patients with chronic cancer pain.Warfield reviewed 10 studies comparing the effectiveness of controlled-release and immediate-release morphine in cancer patients with chronic pain.t The studies that were reviewed were double blinded. How would you double blind such
What is the general goal of a statistical survey?
What is the general goal of a comparative statistical study?
List the advantages of sampling.
Define the term simple random sample (SRS).
What is sampling independence?
What is a sampling fraction?
What is sampling bias?
Provide examples of sampling bias.
What is a probability sample?
Why are “like-to-like comparisons” important in comparative studies?
What is the key distinction between experimental studies and observational studies?
What is a placebo?
What is the placebo effect?
A study seeks to determine the effect of postmenopausal hormone use on mortality. What is the explanatory variable in this study? What is the response variable?
Select the best response: This is the mixing-up of the effects of the explanatory factor with that of extraneous “lurking” variables.(a) the placebo effect(b) blinding(c) confounding
Select the best response: An individual who participates in a statistical study is often referred to as a(a) study subject(b) study factor(c) study treatment
Select the best response: A particular set of explanatory factors applied in an experiment is called a(a) subject(b) factor(c) treatment
What do we call a trial in which the assignment of the treatment type is based on chance?
How does randomization produce comparability?
What does the term blinding refer to in statistical studies?
Who is usually “kept in the dark” in double-blinded studies?
What does equipoise mean?
What does IRB stand for?
Campus survey. A researcher conducts a survey to learn about the sexual behavior of college students on a particular campus. A list of the undergraduates at the university is used to select participants. The investigator sends out 500 surveys but only 136 are returned.(a) Consider how the low
Sampling nurses. You want to survey nurses who work at a particular hospital. Of the 90 nurses who work at this hospital, 40 work in the maternity ward, 20 work in the oncology ward, and 30 work in the surgical ward. You decide to study 10% of the nurse population so you choose nine nurses as
Telephone directory sampling frame. Telephone surveys may use a telephone directory to identify individuals for study. Speculate on the type of household that would be undercovered by using this sampling frame.
Random-digit dialing. Random-digit dialing is often used to select telephone survey samples. This technique randomly selects the last four digits of a telephone number from a telephone exchange. (An exchange is the first three telephone numbers after the area code.)This type of sample gets around
Four-naughts. Could the number “0000” appear in a table of random digits? If so, how likely is this?
Class survey. A simple random sample of students is selected from students attending a class. Identify a problem with this sampling method.
Employee counseling. An employer offers its employees a program that will provide up to four free psychological counseling sessions per calendar year. To evaluate satisfaction with this service, the counseling office mails questionnaires to every 10th employee who used the benefit in the prior
How much do Master of Public Health (MPH) students earn? We are all very concerned with the rising cost of higher education and the amount of money that many students must borrow to complete their studies. A university official wants to know how much MPH students earn from employment during the
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