ALL Available Questions

Table 2 from Hodgson and Cutler (1997) is reproduced in Table 13–3. Which variable is most closely associated with anticipatory dementia?

CES-D

Psych symptoms

Life satisfaction

Health status

Henderson and colleagues (1997) studied a community sample of elderly subjects for a period of 3–4 years. One of their goals was to predict the level of depression, as measured by a depression score, at the end of the study period. Table 13–4 gives the list of measures used in their analysis. What type of statistical method was used to produce this information?

Multiple regression

Logistic regression

Cox proportional hazard model

Paired t tests

Wilcoxon signed rank test

Henderson and colleagues (1997) studied a community sample of elderly subjects for a period of 3–4 years. One of their goals was to predict the level of depression, as measured by a depression score, at the end of the study period. Table 13–4 gives the list of measures used in their analysis. Which set of variables increased the prediction of depression score by the largest amount?

Sociodemographic variables

Age

Psychological health variables

Physical health variables

ADL at wave 2

In a study of mortality from selected diseases in England and Wales by Barker (1989), the author stated that the trend in deaths from thyrotoxicosis rose to a peak in the 1930s and declined thereafter. A graph from this investigation is given in Figure 13–2. Based on this figure, which of the following statements is true?

Iodine deficiency during childhood was not a problem among people born in Britain in the 1800s.

Age-specific rates of thyrotoxicosis rose progressively beginning in 1836 and reached a peak in 1880.

People who are iodine-deficient in youth are more able to adapt to increased iodine intake in later life.

People exposed to increased levels of iodine during their adult years are more likely to develop thyrotoxicosis.

In a sample of 49 individuals, the mean total leukocyte count is found to be 7600 cells/mm3, with a standard deviation of 1400 cells/mm3. If it is reasonable to assume that total leukocyte counts follow a normal distribution, then approximately 50% of the individuals will have a value

Between 6200 and 9000

Between 7400 and 7800

Below 6200 or above 9000

Below 7600

Above 9000

In a sample of 49 individuals, the mean total leukocyte count is found to be 7600 cells/mm3, with a standard deviation of 1400 cells/mm3. Assuming a normal distribution of total leukocyte counts, a randomly selected individual has a total leukocyte count lower than 4800 cells/mm3

1% of the time

2.5% of the time

5% of the time

10% of the time

16.5% of the time

If the correlation between two measures of functional status is 0.80, we can conclude that

The value of one measure increases by 0.80 when the other measure increases by 1.

64% of the observations fall on the regression line.

80% of the observations fall on the regression line.

80% of the variation in one measure is accounted for by the other.

64% of the variation in one measure is accounted for by the other.

An evaluation of an antibiotic in the treatment of possible occult bacteremia was undertaken. Five hundred children with fever but no focal infection were randomly assigned to the antibiotic or to a placebo. A blood sample for culture was obtained prior to beginning therapy, and all patients were reevaluated after 48 h. The design used in this study is best described as a

Randomized clinical trial

Placebo-controlled trial

Controlled clinical trial

Cohort study

Crossover study

An evaluation of an antibiotic in the treatment of possible occult bacteremia was undertaken. Five hundred children with fever but no focal infection were randomly assigned to the antibiotic or to a placebo. A blood sample for culture was obtained prior to beginning therapy, and all patients were reevaluated after 48 h. The authors reported the proportion of children with major infectious morbidity among those with bacteremia was 13% in the placebo group and 10% in the antibiotic group. The 95% confidence interval for the difference in proportions was –2.6% to +8.6%. Thus, the most important conclusion is that

The difference in major infectious morbidity between placebo and antibiotic is statistically significant.

The proportion of children with major infectious morbidity is the same with placebo and antibiotic.

No statistically significant difference exists in the proportions that received placebo and antibiotic.

The study has low power to detect a difference owing to the small sample size, and no conclusions should be drawn until a larger study is done.

Using a chi-square test to determine significance is preferable to determining a confidence interval for the difference.

An evaluation of an antibiotic in the treatment of possible occult bacteremia was undertaken. Five hundred children with fever but no focal infection were randomly assigned to the antibiotic or to a placebo. A blood sample for culture was obtained prior to beginning therapy, and all patients were reevaluated after 48 h. What is the approximate number needed to treat to prevent one patient from developing occult bacteremia?

15

6.7 or 7

65

3

33.3 or 33

Maisel and colleagues (2002) conducted a multinational trial to evaluate the use of B-type natriuretic peptide measurements in the diagnosis of CHF. Patients complaining of shortness of breath were evaluated in the emergency department; physicians assessed the probability that the patient had CHF without knowledge of the results of measurement of B-type natriuretic peptide. Refer to Figure 13–3 for a boxplot of the distributions of B-type natriuretic (pg/mL) for patients in the four New York Heart Association Functional Classifications (based on limitations in physical activity, fatigue, and dyspnea).

What is the estimated median B-type natriuretic for patients in class II?

>1000

Approximately 500

Approximately 300

500 – 100 = 400

1000 – 50 = 950

Maisel and colleagues (2002) conducted a multinational trial to evaluate the use of B-type natriuretic peptide measurements in the diagnosis of CHF. Patients complaining of shortness of breath were evaluated in the emergency department; physicians assessed the probability that the patient had CHF without knowledge of the results of measurement of B-type natriuretic peptide. Refer to Figure 13–3 for a boxplot of the distributions of B-type natriuretic (pg/mL) for patients in the four New York Heart Association Functional Classifications (based on limitations in physical activity, fatigue, and dyspnea).

The statistical method most appropriate to analyze the means of the four groups is

Analysis of variance

Correlation

Independent groups t test

Simple linear regression

Trend analysis

A study of fluctuation in body weight and health outcomes using data on participants in the Framingham study was undertaken (Lissner et al, 1991). The investigators used body mass index (BMI) values from the first eight biennial examinations during the study plus the subject’s recalled weight at age 25 to determine three measures for each subject: mean BMI, linear trend of BMI, and coefficient of variation. Table 13–5 presents the regression coefficients and P values for level, slope, and coefficient of variation (CV) of BMI in predicting total mortality, morbidity and mortality from coronary heart disease, and morbidity from cancer for men and women separately.

The dependent variable best predicted for men was

Total mortality

Morbidity due to coronary heart disease (CHD)

Mortality from CHD

Morbidity due to cancer

Impossible to determine

A study of fluctuation in body weight and health outcomes using data on participants in the Framingham study was undertaken (Lissner et al, 1991). The investigators used body mass index (BMI) values from the first eight biennial examinations during the study plus the subject’s recalled weight at age 25 to determine three measures for each subject: mean BMI, linear trend of BMI, and coefficient of variation. Table 13–5 presents the regression coefficients and P values for level, slope, and coefficient of variation (CV) of BMI in predicting total mortality, morbidity and mortality from coronary heart disease, and morbidity from cancer for men and women separately.

The measure of BMI most important in predicting outcomes for women was

Level of BMI

Slope of BMI

CV of BMI

Impossible to determine

A study of fluctuation in body weight and health outcomes using data on participants in the Framingham study was undertaken (Lissner et al, 1991). The investigators used body mass index (BMI) values from the first eight biennial examinations during the study plus the subject’s recalled weight at age 25 to determine three measures for each subject: mean BMI, linear trend of BMI, and coefficient of variation. Table 13–5 presents the regression coefficients and P values for level, slope, and coefficient of variation (CV) of BMI in predicting total mortality, morbidity and mortality from coronary heart disease, and morbidity from cancer for men and women separately.

The BMI variable with the widest 95% confidence interval is

Level of BMI for morbidity due to CHD in men

Slope of BMI for predicting total mortality in women

CV of BMI for predicting morbidity due to cancer in women

CV of BMI for predicting total mortality in men

Impossible to determine

A study of fluctuation in body weight and health outcomes using data on participants in the Framingham study was undertaken (Lissner et al, 1991). The investigators used body mass index (BMI) values from the first eight biennial examinations during the study plus the subject’s recalled weight at age 25 to determine three measures for each subject: mean BMI, linear trend of BMI, and coefficient of variation. Table 13–5 presents the regression coefficients and P values for level, slope, and coefficient of variation (CV) of BMI in predicting total mortality, morbidity and mortality from coronary heart disease, and morbidity from cancer for men and women separately.

The legend to Table 13–5 says that these results are for a model that included five risk factors in addition to age and the three BMI variables. The main purpose for using this model is to

Include all relevant risk factors

Determine the effect of BMI variables controlling for risk factors

Determine if differences exist between men and women once risk factors are included

Determine if the risk factors are important

Table 1 from the study of glucose tolerance and insulin sensitivity in normal and overweight hyperthyroid women is reproduced below in Table 13–6 (Gonzalo et al, 1996). Which statistical procedure is best if the authors wanted to compare the baseline glucose (mmol/L) in the women to see if weight or thyroid level have an effect?

Correlation

Independent-groups t test

Paired t test

One-way ANOVA

Two-way ANOVA

If the relationship between two measures is linear and the coefficient of determination has a value near 1, a scatterplot of the observations

Is a horizontal straight line

Is a vertical straight line

Is a straight line that is neither horizontal nor vertical

Is a random scatter of points about the regression line

Has a positive slope

A study was undertaken to evaluate the use of computed tomography (CT) in the diagnosis of lumbar disk herniation. Eighty patients with lumbar disk herniation confirmed by surgery were evaluated with CT, as were 50 patients without herniation. The CT results were positive in 56 of the patients with herniation and in 10 of the patients without herniation. The sensitivity of CT for lumbar disk herniation in this study is

10/50, or 20%

24/80, or 30%

56/80, or 70%

40/50, or 80%

56/66, or 85%

A study was undertaken to evaluate the use of computed tomography (CT) in the diagnosis of lumbar disk herniation. Eighty patients with lumbar disk herniation confirmed by surgery were evaluated with CT, as were 50 patients without herniation. The CT results were positive in 56 of the patients with herniation and in 10 of the patients without herniation. The false-positive rate in this study is

10/50, or 20%

24/80, or 30%

56/80, or 70%

40/50, or 80%

56/66, or 85%

A study was undertaken to evaluate the use of computed tomography (CT) in the diagnosis of lumbar disk herniation. Eighty patients with lumbar disk herniation confirmed by surgery were evaluated with CT, as were 50 patients without herniation. The CT results were positive in 56 of the patients with herniation and in 10 of the patients without herniation. Computed tomography is used in a patient who has a 50–50 chance of having a herniated lumbar disk, according to the patient’s history and physical examination. What are the chances of herniation if the CT is positive?

35/100, or 35%

50/100, or 50%

35/50, or 70%

40/55, or 73%

35/45, or 78%

A study was undertaken to evaluate the use of computed tomography (CT) in the diagnosis of lumbar disk herniation. Eighty patients with lumbar disk herniation confirmed by surgery were evaluated with CT, as were 50 patients without herniation. The CT results were positive in 56 of the patients with herniation and in 10 of the patients without herniation. The likelihood ratio is

0.28

0.875

1.0

3.5

7.0

In a placebo-controlled trial of the use of oral aspirin–dipyridamole to prevent arterial restenosis after coronary angioplasty, 38% of patients receiving the drug had restenosis, and 39% of patients receiving placebo had restenosis. In reporting this finding, the authors stated that P > 0.05, which means that

Chances are greater than 1 in 20 that a difference would again be found if the study were repeated.

The probability is less than 1 in 20 that a difference this large could occur by chance alone.

The probability is greater than 1 in 20 that a difference this large could occur by chance alone.

Treated patients were 5% less likely to have restenosis.

The chance is 95% that the study is correct.

A study of the relationship between the concentration of lead in the blood and hemoglobin resulted in the following prediction equation: Y = 15 – 0.1(X), where Y is the predicted hemoglobin and X is the concentration of lead in the blood. From the equation, the predicted hemoglobin for a person with blood lead concentration of 20 mg/dL is

13

14.8

14.9

15

20

D’Angio and colleagues (1995) studied a group of extremely premature infants to learn whether they have immunologic responses to tetanus toxoid and polio vaccines that are similar to the response of full-term infants. Figure 1 from their study contains the plots of the antitetanus titers before and after the vaccine was given (reproduced in Figure 13–4). The authors calculated the geometric means. Which statistical test is best to learn if the titer level increases in the preterm group after they were given the vaccine?

One-group t test

Paired t test

Wilcoxon signed rank test

Two independent-groups t test

Wilcoxon rank sum test

D’Angio and colleagues (1995) studied a group of extremely premature infants to learn whether they have immunologic responses to tetanus toxoid and polio vaccines that are similar to the response of full-term infants. Figure 1 from their study contains the plots of the antitetanus titers before and after the vaccine was given (reproduced in Figure 13–4). The authors calculated the geometric means. Based on Figure 13–4, which is the appropriate conclusion?

No difference exists between preterm and full-term infants before and after the vaccine.

No difference exists between preterm and full-term infants before the vaccine, but a difference does occur after the vaccine.

A difference exists between preterm and full-term infants before and after the vaccine.

A difference exists between preterm and full-term infants before the vaccine but not after.

Figure 13–5 summarizes the gender-specific distribution of values on a laboratory test.

From Figure 13–5, we can conclude that

Values on the laboratory test are lower in men than in women.

The distribution of laboratory values in women is bimodal.

Laboratory values were reported more often for women than for men in this study.

Half of the men have laboratory values between 30 and 43.

The standard deviation of laboratory values is equal in men and women.

Figure 13–5 summarizes the gender-specific distribution of values on a laboratory test.

The most appropriate statistical test to compare the distribution of laboratory values in men with that in women is

Chi-square

Paired t test

Independent-groups t test

Correlation

Regression

A study was undertaken to evaluate any increased risk of breast cancer among women who use birth control pills. The relative risk was calculated. A type I error in this study consists of concluding

A significant increase in the relative risk when the relative risk is actually 1

A significant increase in the relative risk when the relative risk is actually greater than 1

A significant increase in the relative risk when the relative risk is actually less than 1

No significant increase in the relative risk when the relative risk is actually 1

No significant increase in the relative risk when the relative risk is actually greater than 1

A graph of the lowest oxyhemoglobin percentage in the patients studied overnight in the study by Good and colleagues (1996) is given in Figure 1 from their article (see Figure 13–6). What is the best way to describe the distribution of these values?

Normal distribution

Chi-square distribution

Binomial distribution

Negatively skewed distribution

Positively skewed distribution

A graph of the lowest oxyhemoglobin percentage in the patients studied overnight in the study by Good and colleagues (1996) is given in Figure 1 from their article (see Figure 13–6).

If the investigators wanted to compare oxyhemoglobin levels in patients who died within 12 months with the levels of oxyhemoglobin percentage in patients who survived, what method should they use?

t test for two independent groups

Wilcoxon rank sum test

Analysis of variance

Chi-square test

Kaplan–Meier curves

The scale used in measuring cholesterol is

Nominal

Ordinal

Interval

Discrete

Qualitative

The scale used in measuring presence or absence of a risk factor is

Binary

Ordinal

Interval

Continuous

Quantitative

Which of the following sources is most likely to provide an accurate estimate of the prevalence of multiple sclerosis (MS) in a community?

A survey of practicing physicians asking how many MS patients they are currently treating

Information from hospital discharge summaries

Data from autopsy reports

A telephone survey of a sample of randomly selected homes in the community asking how many people living in the home have the disease

Examination of the medical records of a representative sample of people living in the community

In an epidemiologic study of carbon-black workers, 500 workers with respiratory disease and 200 workers without respiratory disease were selected for study. The investigators obtained a history of exposure to carbon-black dust in both groups of workers. Among workers with respiratory disease, 250 gave a history of exposure to carbon-black dust; among the 200 workers without respiratory disease, 50 gave a history of exposure. The odds ratio is

1.0

1.5

2.0

3.0

Cannot be determined from the preceding information

In an epidemiologic study of carbon-black workers, 500 workers with respiratory disease and 200 workers without respiratory disease were selected for study. The investigators obtained a history of exposure to carbon-black dust in both groups of workers. Among workers with respiratory disease, 250 gave a history of exposure to carbon-black dust; among the 200 workers without respiratory disease, 50 gave a history of exposure. This study is best described as a

Case–control study

Cohort study

Cross-sectional study

Controlled experiment

Randomized clinical trial

A physician wishes to study whether a particular risk factor is associated with some disease. If, in reality, the presence of the risk factor leads to a relative risk of disease of 4.0, the physician wants to have a 95% chance of detecting an effect this large in the planned study. This statement is an illustration of specifying

A null hypothesis

A type I, or alpha, error

A type II, or beta, error

Statistical power

An odds ratio

The most likely explanation for a lower crude annual mortality rate in a developing country than in a developed country is that the developing country has

An incomplete record of deaths

A younger age distribution

An inaccurate census of the population

A less stressful life-style

Lower exposure to environmental hazards

The distribution of variation in heart rate to deep breathing and the Valsalva ratio from the study by Gelber and colleagues (1997) is given in Figure 1 in their article and is reproduced below in Figure 13–7. What is the best way to describe the distribution of these values?

Normal distribution

Chi-square distribution

Binomial distribution

Negatively skewed distribution

Positively skewed distribution

The distribution of variation in heart rate to deep breathing and the Valsalva ratio from the study by Gelber and colleagues (1997) is given in Figure 1 in their article and is reproduced below in Figure 13–7. What is the best method to find the normal range of values for the Valsalva ratio?

The values determined by the mean ± 2 standard deviations

The values determined by the mean ± 2 standard errors

The values determined by the upper and lower 5% of the distribution

The values determined by the upper and lower 2½% of the distribution

The highest and lowest values defined by the whiskers on a box plot

A study of the exercise tolerance test for detecting coronary heart disease had the characteristics shown in Table 13–7.

The authors concluded the exercise stress test has positive predictive value in excess of 75%. The error in this conclusion is that

Not enough patients are included in the study for precise estimates.

The sample sizes should be equal in these kinds of studies.

The positive predictive value is really 80%.

The prevalence of coronary heart disease (CHD) is assumed to be 33%.

No gold standard exists for D.

Hébert and colleagues (1997) studied functional decline in a very elderly population of community-dwelling subjects. They used the Functional Autonomy Measurement System (SMAF) questionnaire to measure several indices of functioning. Figure 2 from their article displays box plots of scores for men and women at baseline and is reproduced in Figure 13–8. Based on the plots, men and women had the most similar scores on which measure?

ADL (adult daily living)

Mobility

Communication

Mental

IADL (instrumental activities of daily living)

Total score

Impossible to tell

Hébert and colleagues (1997) studied functional decline in a very elderly population of community-dwelling subjects. They used the Functional Autonomy Measurement System (SMAF) questionnaire to measure several indices of functioning. Figure 2 from their article displays box plots of scores for men and women at baseline and is reproduced in Figure 13–8. Among men, which measure has the most symmetric distribution?

ADL (adult daily living)

Mobility

Communication

Mental

IADL (instrumental activities of daily living)

Total score

Impossible to tell

Hébert and colleagues (1997) studied functional decline in a very elderly population of community-dwelling subjects. They used the Functional Autonomy Measurement System (SMAF) questionnaire to measure several indices of functioning. Figure 2 from their article displays box plots of scores for men and women at baseline and is reproduced in Figure 13–8. What is the median mental score for women?

0

0.15

0.3

0.7

Impossible to tell

Several studies have shown that men with a low blood cholesterol level as well as those with high levels have an increased risk of early death. A report in the March 21, 1993, New York Times described a study by Dr Carlos Iribarren at the University of Southern California on a cohort of 8000 Japanese-American men followed for 23 years. The purpose was to study further the link between low blood cholesterol levels and higher death rate. The men were divided into four groups: healthy men, men with chronic disorders of the stomach or liver, heavy smokers, and heavy drinkers. Within each group, subjects were stratified according to their cholesterol level. Among men with cholesterol levels below 189 mg/dL, death rates were higher in the chronic illness, heavy smoker, and heavy drinker groups but not in the group of healthy men.

This study highlights a potential threat that may have occurred in previous studies that suggested that low cholesterol is linked to higher death rates. The most likely threat in the previous studies is

Selection bias

Length of follow-up

A confounding variable

Inappropriate sample size

Several studies have shown that men with a low blood cholesterol level as well as those with high levels have an increased risk of early death. A report in the March 21, 1993, New York Times described a study by Dr Carlos Iribarren at the University of Southern California on a cohort of 8000 Japanese-American men followed for 23 years. The purpose was to study further the link between low blood cholesterol levels and higher death rate. The men were divided into four groups: healthy men, men with chronic disorders of the stomach or liver, heavy smokers, and heavy drinkers. Within each group, subjects were stratified according to their cholesterol level. Among men with cholesterol levels below 189 mg/dL, death rates were higher in the chronic illness, heavy smoker, and heavy drinker groups but not in the group of healthy men.

Using the guidelines in Table 10–2, select the most appropriate statistical method to analyze the data collected in this study.

Mantel–Haenszel chi-square

ANOVA

Multiple regression

Log-linear methods

Figure 2 in Dennison and colleagues (1997) shows the relationship between the age of children and daily consumption of fruit juice (see Figure 13–9). What is the best method to learn if a difference exists between 2-year-old and 5-year-old children?

Chi-square test

Fisher’s exact test

Fisher’s z distribution

Paired t test

Pearson correlation

Figure 2 in Dennison and colleagues (1997) shows the relationship between the age of children and daily consumption of fruit juice (see Figure 13–9). What is the best way to describe the magnitude of the relationship between the age of children and daily consumption of fruit juice?

Kappa

Odds ratio

Pearson correlation

Spearman correlation

r2

Birth weights of a population of infants at 40 weeks gestational age are approximately normally distributed, with a mean of 3000 g. Roughly 68% of such infants weigh between 2500 and 3500 g at birth. If a sample of 100 infants were studied, the standard error would be

50

100

250

500

None of the above

A significant positive correlation has been observed between alcohol consumption and the level of systolic blood pressure in men. From this correlation, we may conclude that

No association exists between alcohol consumption and systolic pressure.

Men who consume less alcohol are at lower risk for increased systolic pressure.

Men who consume less alcohol are at higher risk for increased systolic pressure.

High alcohol consumption can cause increased systolic pressure.

Low alcohol consumption can cause increased systolic pressure.

In a randomized trial of patients who received a cadaver renal transplant, 100 were treated with cyclosporin and 50 were treated with conventional immunosuppression therapy. The difference in treatments was not statistically significant at the 5% level. Therefore

This study has proven that cyclosporin is not effective.

Cyclosporin could be significant at the 1% level.

Cyclosporin could be significant at the 10% level.

The groups have been shown to be the same.

The treatments should not be compared because of the differences in the sample sizes.

The statistical method used to develop guidelines for diagnostic-related groups (DRGs) was

Survival analysis

t tests for independent groups

Multiple regression

Analysis of covariance

Correlation

Suppose the confidence limits for the mean of a variable are 8.55 and 8.65. These limits are

Less precise but have a higher confidence than 8.20 and 9.00

More precise but have a lower confidence than 8.20 and 9.00

Less precise but have a lower confidence than 8.20 and 9.00

More precise but have a higher confidence than 8.20 and 9.00

Indeterminate because the level of confidence is not specified

A senior medical student wants to plan her elective schedule. The probability of getting an elective in endocrinology is 0.8, and the probability of getting an elective in sports medicine is 0.5. The probability of getting both electives in the same semester is 0.4. What is the probability of getting into endocrinology or sports medicine or both?

0.4

0.5

0.8

0.9

1.7

A manager of a multispecialty clinic wants to determine the proportion of patients who are referred by their primary care physician to another physician within the group versus a physician outside the group. Every 100th patient chart is selected and reviewed for a letter from a physician other than the primary care physician. This procedure is best described as

Random sampling

Stratified sampling

Quota sampling

Representative sampling

Systematic sampling

The probability is 0.6 that a medical student will receive his first choice of residency programs. Four senior medical students want to know the probability that they all will obtain their first choice. The solution to this problem is best found by using

The binomial distribution

The normal distribution

The chi-square distribution

The z test

Correlation

The graph in Figure 13–10 gives the 5-year survival rates for patients with cancer at various sites. From this figure, we can conclude

That breast and uterine corpus cancer are increasing at higher rates than other cancers

That lung cancer is the slowest growing cancer

That few patients are diagnosed with distant metastases

That survival rates for patients with regional involvement are similar, regardless of the primary site of disease

None of the above

Table 3 from Shlipak and colleagues (1999) provides diagnostic test characteristics of electrocardiographic criteria for determining myocardial infarction (MI) (see Table 13–8). Which of the following five features is the best single feature for ruling in MI?

ST elevation ≥ 5 mm

Overall ECG algorithm

QRS notching

RS complex in lead V8

Sign of Cabrera

Table 3 from Shlipak and colleagues (1999) provides diagnostic test characteristics of electrocardiographic criteria for determining myocardial infarction (MI) (see Table 13–8). Which of the following five features is the best single feature for ruling out MI?

ST elevation ≥ 5 mm

Overall ECG algorithm

QRS notching

RS complex in lead V8

Sign of Cabrera

A study was undertaken to compare treatment options in black and white patients who are diagnosed as having breast cancer. The 95% confidence interval for the odds ratio for blacks being more likely to be untreated than whites was 1.1 to 2.5. The statement that most accurately describes the meaning of these limits is that

Ninety-five percent of the odds ratios fall within these limits.

Black women are up to 2.5 times more likely than whites to be untreated.

Ninety-five percent of the time blacks are more likely than whites to be untreated.

Blacks are 95 times more likely than whites to receive no treatment for breast cancer.

No difference exists in the treatment of black and white women.

In the study to identify risk factors for discontinuing dialysis, Bajwa and colleagues (1996) presented information on the sociodemographic characteristics of patients in the study (Table 2 from Bajwa is reproduced in Table 13–9).

Which of these characteristics has the greatest statistical significance in identifying those who stopped versus those who continued on dialysis?

Sex

Age

Marital status

Treatment

Education

In the study to identify risk factors for discontinuing dialysis, Bajwa and colleagues (1996) presented information on the sociodemographic characteristics of patients in the study (Table 2 from Bajwa is reproduced in Table 13–9).

What statistical technique can the investigators use to control for differences in any of the sociodemographic characteristics in the two groups that might confound the statistical analysis of mortality?

Paired t test

Analysis of variance

Chi-square

Regression

Logistic regression

The results of the multivariate analysis to predict stopping dialysis from the study by Bajwa and colleagues (1996) is given in Table 13–10. All of the independent variables were coded as yes or no. The regression coefficient for severe pain is –1.20 and for comorbidity is 0.79. Why is the P value for comorbidity lower than the P value for severe pain?

The standard error for comorbidity is smaller.

The relationship between stopping dialysis and comorbidity is positive.

The relative risk associated with comorbidity is higher.

Comorbidity is a more objective measure.

Physicians wish to determine whether the emergency department (ED) at the local hospital is being overused by patients with minor health problems. A random sample of 5000 patients was selected and categorized by age and degree of severity of the problem that brought them to the ED; severity was measured on a scale of 1 to 3, with 3 being most severe; the results are given in Table 13–11.

The joint probability that a 3-year-old patient with a problem of high severity is selected for review is

200/5000 = 0.04

200/1600 = 0.125

1600/5000 = 0.32

1100/5000 = 0.22

1600/5000 + 1100/5000 = 0.54

Physicians wish to determine whether the emergency department (ED) at the local hospital is being overused by patients with minor health problems. A random sample of 5000 patients was selected and categorized by age and degree of severity of the problem that brought them to the ED; severity was measured on a scale of 1 to 3, with 3 being most severe; the results are given in Table 13–11.

If a patient comes to the ED with a problem of low severity, how likely is it that the patient is older than 14 years of age?

1700/5000 × 2200/5000 = 0.15

600/2200 = 0.27

1700/5000 = 0.34

600/1700 = 0.35

2200/5000 = 0.44