A case control study is described as _____ (experimental/observational) and _____ (prospective/retrospective).
Observational; retrospective
A cohort study is described as _____ (experimental/observational) and _____ (prospective/retrospective).
Observational; prospective
What type of epidemiologic study selects subjects on the basis of the presence or absence of disease?
A case control study; subjects with the disease are the cases and those without are the controls
What type of epidemiologic study reports an odds ratio in its conclusions?
Case control study
What type of measure does a case control study use to report its conclusions?
Odds ratio
True or False? In a cohort study, the subjects are chosen on the basis of the presence or absence of risk factors.
TRUE
True or False? In a cohort study, the subjects are chosen on the basis of the presence or absence of disease.
False; subjects are chosen on the basis of presence or absence of risk factors
True or False? A cohort study follows subjects over a period of time to study the development of disease.
TRUE
What type of epidemiologic study selects subjects on the basis of their exposure to risk factors?
Cohort study
What type of epidemiologic study follows subjects over time to study the development of disease?
Cohort study
What type of epidemiologic study reports relative risk as an outcome measure?
Cohort study
What type of measure does a cohort study use to report its conclusions?
Relative risk
What type of research study is defined as a collection of data from a group of people to assess the frequency of disease (and related risk factors) at a certain point in time?
A cross-sectional study
True or False? A cross-sectional research study can indicate disease prevalence.
TRUE
True or False? A cross-sectional research study can show the correlation of a risk with a disease.
True; however, it cannot show causality
What type of research study compares the frequency with which monozygotic twins develop a disease with how often it develops in dizygotic twins?
A twin concordance study
What aspect of risk for development of disease can be assessed with a twin concordance study?
The heritability of a disease
What type of research study compares the frequency with which siblings raised in different homes develop a trait or disease?
An adoption study
What does an adoption study measure?
The influence of genes and environment on traits and diseases
Patients with COPD had higher odds of a history of smoking than those without COPD is an example of _____ (odds ratio/relative risk).
Odds ratio
Smokers had a higher risk of developing COPD than did nonsmokers is an example of _____ (odds ratio/relative risk).
Relative risk
Are clinical trials experimental or observational studies?
Experimental
What type of epidemiologic study compares the therapeutic benefits of different treatment conditions or of treatment and placebo?
Clinical trial
What three features can be introduced into the design of a clinical trial to enhance the quality of the study?
It can be randomized, controlled, and double-blinded
What is the study population for a phase I clinical trial?
A small number of healthy volunteers
Among whom is a phase III clinical trial performed?
A larger number of patients with the disease of interest randomly assigned to either the treatment under investigation or the best available treatment (or placebo)
What is the purpose of a phase I clinical trial?
To establish the safety, toxicity, and pharmacokinetics of a new treatment
What is the purpose of a phase II clinical trial?
To establish the safe/efficacious dosing of a new treatment, as well as possible adverse effects
What feature of a study can make a phase III clinical trial more convincing?
Making the trial double-blinded, so that neither the patient nor the investigator knows if the patient is in the treatment or control group
True or False? A clinical trial is a type of observational study.
False; a clinical trial is a type of experimental study
True or False? A clinical trial can compare the therapeutic benefits of two or more treatments or of a treatment and a placebo.
TRUE
What is the purpose of a phase III clinical trial?
To compare the new treatment with existing treatments and determine whether the treatment will be approved for use
What are two factors that may limit the reliability of a meta-analysis?
The quality of the individual studies or bias in the selection of studies for analysis
What type of epidemiologic study pools data from several published studies to achieve greater statistical power?
Meta-analysis
True or False? A meta-analysis is the highest echelon of clinical evidence.
TRUE
Given that predictive values of a test for a disease are dependent on the prevalence of the disease, how does a low prevalence of disease affect the positive predictive value of the test?
The positive predictive value of the test is lower for a disease with a lower prevalence
True or False? Positive and negative predictive values of a test for a disease depend on the prevalence of the disease in the population being tested.
TRUE
Given that predictive values of a test for a disease depend on the prevalence of the disease, how does a high prevalence of disease affect the positive predictive value of the test?
The positive predictive value of the test is higher for a disease with higher prevalence
If a diagnostic test has 100% sensitivity, what should the value of the false-negative rate equal?
The value of the false-negative rate should be equal to 0; all cases of the disease are detected by the test
If a diagnostic test has 100% specificity, what should the value of the false-positive rate equal?
The value of the false-positive rate should be equal to 0; all patients without the disease are correctly identified
In HIV testing, enzyme-linked immunosorbent assay screening is _____ (sensitive/specific) and has a high false-_____ (negative/positive) rate, with a _____ (high/low) threshold.
Sensitive; positive; low
In HIV testing, Western blot testing is _____ (sensitive/specific) and has a high false-_____ (negative/positive) rate, with a _____ (high/low) threshold.
Specific; negative; high
How is the sensitivity of a test determined?
Sensitivity is the number of cases correctly identified by a test divided by the total number of cases of the disease
What epidemiologic measurement is equal to the probability of a positive test (given that a person has the disease)?
Sensitivity
Given the sensitivity of a test for a particular disease, how is the false-negative rate calculated?
False-negative rate = 1 - sensitivity
Should the sensitivity of a screening test be high or low?
High
True or False? A screening test is a good method for ruling out a diagnosis, because it is a test with high sensitivity.
True (SNOUT = SeNsitivity rules OUT)
How is the specificity of a test determined?
Specificity is the number of correctly identified patients without the disease divided by the total number of those without the disease
What epidemiologic measurement is equal to the probability of a negative test (given that a person is free of the disease)?
Specificity
Given the specificity of a test for a particular disease, how is the false-positive rate calculated?
False-positive rate = 1 - specificity
For a confirmatory test, should the specificity of the test be high or low?
High
True or False? A confirmatory test is an appropriate method for ruling in a diagnosis, because it is a test with high specificity.
True (SPIN = SPecificity rules IN)
How is the positive predictive value of a test determined?
Positive predictive value is the number of true positive results divided by the total number of positive results
When calculating the positive predictive value of a test for a disease, what is the number of true positives divided by?
The number of people who tested positive for the disease
What epidemiologic measurement is equal to the probability of having a condition (given a positive test)?
Positive predictive value
How is negative predictive value of a test determined?
Negative predictive value is the number of true negative results divided by the total number of negative results
When calculating the negative predictive value of a test for a disease, what is the number of true negatives divided by?
The number of people who tested negative for the disease
What epidemiologic measurement is equal to the probability of not having the condition (given a negative test)?
Negative predictive value
Given that predictive values of a test for a disease are dependent on the prevalence of the disease, how does a high prevalence of disease affect the negative predictive value of the test?
The negative predictive value of the test is lower for a disease with a higher prevalence
Given that predictive values of a test for a disease are dependent on the prevalence of the disease, how does a low prevalence of disease affect the negative predictive value of the test?
The negative predictive value of the test is higher for a disease with a lower prevalence
In HIV testing, enzyme-linked immunosorbent assay is used as a screening test. Is a high sensitivity or high specificity ideal for this purpose?
Sensitivity
In HIV testing, the Western blot is used to confirm an initial screening test. Is a high sensitivity or specificity ideal for this purpose?
Specificity
In epidemiology, what measure of disease frequency is calculated by dividing the total number of cases in the population at a given time by the total population at risk?
Point prevalence
In epidemiology, what measure of disease frequency is calculated by dividing the number of new cases in the population during a given time period by the total population at risk during that time?
Incidence (Incidence is new incidents)
To estimate the prevalence of a disease, the incidence of the disease is multiplied by what factor?
The disease duration
In chronic disease states such as diabetes, is the prevalence of disease greater than, less than, or equal to the incidence?
Prevalence is much greater than annual incidence because of the long duration of the disease
In acute disease states such as a common cold, is the prevalence of disease greater than, less than, or equal to the incidence?
Incidence and prevalence are approximately equal for diseases of short duration
True or False? When calculating the incidence of a disease, people who were previously positive for the disease are no longer considered to be at risk.
TRUE
True or False? When calculating the incidence of a disease, the total population at risk during a certain time period should include people who have the disease.
False; the total population at risk during a certain period should not include people who have the disease because incidence is a measure of new cases of a disease, and those who have the disease are not at risk of getting the disease
When calculating the odds ratio for a disease on the basis of exposure to a risk factor, what factor is divided by the odds of having the disease in an unexposed group?
The odds of having the disease in an exposed group
When calculating the odds ratio for a disease on the basis of exposure to a risk factor, the odds of having the disease in an exposed group is divided by what factor?
The odds of having the disease in an unexposed group
True or False? The odds ratio for a disease based on exposure to a risk factor approximates the relative risk if the prevalence of the disease is low.
TRUE
True or False? The odds ratio for a disease based on exposure to a risk factor approximates the relative risk if prevalence of the disease is high.
False; the odds ratio approximates the relative risk if the prevalence of the disease is low
When calculating the relative risk for a disease on the basis of exposure to a risk factor, what factor is divided by the disease risk in an unexposed group?
The disease risk in an exposed group
When calculating the relative risk for a disease on the basis of exposure to a risk factor, the disease risk in an exposed group is divided by what factor?
The disease risk in an unexposed group
What epidemiologic measurement is equal to the difference in disease incidence in an exposed group and an unexposed group?
Attributable risk; it is the percentage of cases of a disease caused by a risk factor
True or False? Attributable risk is the difference in risk between exposed and unexposed groups.
TRUE
What term describes the proportion of disease caused by exposure to the risk factor being studied?
Attributable risk
How is the number needed to treat calculated?
1/absolute risk reduction
How is the number needed to harm calculated?
1/attributable risk
What term refers to the consistency and reproducibility of a test (reliability) and the absence of random variation in a test?
Precision
What term refers to the trueness of test measurements (validity)?
Accuracy
What type of error reduces precision in a test?
Random error
What type of error reduces accuracy in a test?
Systematic error
What type of bias occurs in epidemiologic studies when subjects are not randomly assigned to a study group?
Selection bias
What type of bias occurs in epidemiologic studies when knowledge of the presence of a disorder alters self-reporting by subjects?
Recall bias
What epidemiologic term refers to a systematically favored outcome in a study?
Bias
What type of bias occurs in epidemiologic studies when subjects are not representative of the population as a whole?
Sampling bias
What are four ways to reduce bias in epidemiologic studies?
Use blind studies (double blind, preferably), assess placebo responses, perform a crossover study, and randomization
What type of bias occurs in epidemiologic studies when information is gathered at an inappropriate time?
Late-look bias
What are two subtypes of a blind study?
Single-blind studies, in which subjects are unaware of their treatment characteristics; and double-blind studies, in which neither the researcher nor the subject is aware of the selection status
What type of bias occurs in epidemiologic studies when subjects in different groups are not treated the same?
Procedure bias; eg, subjects in a treatment group are encouraged to have better compliance than those in a control group
What is the design of a crossover study?
The subject acts as his or her own control and is subjected to both treatment and placebo at different times
What type of bias occurs in epidemiologic studies when there are two closely associated factors and therefore the effect of one factor can change or confuse the effect of the other?
Confounding bias; in which the causal relationship is better explained by a variable other that the one being studied
What type of bias occurs in epidemiologic studies when early detection is confused with increased survival?
Lead-time bias
What is the name of the phenomenon whereby a researcher’s belief in the efficacy of a treatment changes the outcome of that treatment?
Pygmalion effect
What type of bias occurs in epidemiologic studies when the group being studied changes its behavior to meet the expectations of the researcher?
Hawthorne effect
In a normal Gaussian distribution, what is the relationship between the mean, the median, and the mode?
Mean = median = mode
What is the shape of the curve in a bimodal distribution?
The curve has two peaks
If the statistical distribution of a data set has a positive skew, on what side of the mean is there a tail?
The right side
If the statistical distribution of a data set has a negative skew, on what side of the mean is there a tail?
The left side
In a data set that has a distribution with a negative skew, what is the relationship between the mean, the median, and the mode?
Mean median mode
In a data set that has a distribution with a positive skew, what is the relationship between the mean, the median, and the mode?
Mean median mode
Which characteristic is least affected by outliers: mean, median, or mode?
Mode
What is the term for the hypothesis that there is no association between the variables being studied?
Null hypothesis
What type of statistical hypothesis postulates that there is some difference between the populations being compared: null or alternative hypothesis?
Alternative hypothesis
In statistical calculations, the P value is equal to the probability of making what type of error?
Type I error (); type I error occurs when it is incorrectly concluded that an association is present
In statistical analyses, the P value is judged against the probability of making a type I error (). What is the standard level of significance for in most contexts?
0.05
In a statistical analysis, if P = .03, what percentage chance is there that the data are showing a difference by chance alone when none truly exists?
3%
What type of statistical error occurs when the null hypothesis is not rejected when it should have been?
Type II error (); type II error occurs when it is falsely concluded that there is no association between variables
What type of statistical error occurs when the experimental hypothesis is mistakenly accepted and the null hypothesis is rejected?
Type I error ()
In statistical analyses, if = 0.2, what percentage chance is there that the null hypothesis has been falsely accepted?
20%; this is generally considered an acceptable level for in a study design
What type of statistical error occurs when one states that there is not an effect or difference when, in fact, one does exist?
Type II error ()
In statistical calculations, the value is equal to the probability of making what type of error?
Type II error ()
The power of a statistical test depends on which three factors?
The total number of end points experienced by the population, the difference in compliance between the treatment groups, and the size of the expected effect
What statistical term refers to the probability of rejecting the null hypothesis when it is in fact false?
Power (or 1 - )
What study parameter is calculated when the probability of making a type II error is subtracted from 1?
Power
How can a scientist increase the power of a proposed study?
By increasing study sample size
How can the standard error of the mean be calculated from the standard deviation?
SEM equals SD over the square root of the sample size
True or False? The standard error of the mean is directly proportional to the standard deviation.
TRUE
True or False? The standard error of the mean is less than σ.
TRUE
In biostatistics, what effect does increasing the sample size have on the standard error of the mean?
The standard error of the mean decreases
In biostatistics, what effect does decreasing the sample size have on the standard error of the mean?
The standard error of the mean increases
In a data set that has a normal (Gaussian) distribution, what percentage of the data falls within one standard deviation of the mean?
68%
In a data set that has a normal (Gaussian) distribution, what percentage of the data falls within two standard deviations of the mean?
95%
In a data set that has a normal (Gaussian) distribution, what percentage of the data falls within three standard deviations of the mean?
99.70%
In biostatistics, how is the confidence interval calculated when the mean, the Z score, and the standard error of the mean are known?
Confidence interval = range from [mean - Z (SEM)] to [mean + Z (SEM)]
For the 95% confidence interval, what is the value of Z?
Z = 1.96
If the confidence interval between two groups overlaps, then these groups _____ (are/are not) significantly different.
Are not
What statistical term refers to the range of values in which a specified probability of the means of repeated samples would be expected to fall?
Confidence interval
In biostatistics, what P value corresponds with a confidence interval of 95%?
0.05
True or False? In biostatistical calculations, the Z value is dependent on the confidence interval desired.
TRUE
If the 95% confidence interval for a mean difference between two variables includes 0, is the null hypothesis rejected?
No, the null hypothesis is not rejected, and there is no significant difference between the two variables
If the 95% confidence interval for an odds ratio or relative risk calculation includes 1, is the null hypothesis rejected?
No, the null hypothesis is not rejected; there is no significant difference between the two groups studied
What type of statistical test is used to check for a difference between the means of three or more groups?
Analysis of variance (also known as ANOVA)
What type of statistical test is used to check for a difference between the means of two groups?
t-test (remember: Mr. T is mean)
What type of statistical test is used to check for a difference between two or more percentages or proportions of categorical outcomes (not mean values)?
χ²
A perfect linear negative correlation between two variables has what correlation coefficient?
1
True or False? r is always between -1 and 1.
TRUE
What statistical term’s absolute value indicates the strength of the correlation between two variables?
Correlation coefficient (r)
In biostatistics, how is the coefficient of determination calculated from the correlation coefficient?
Coefficient of determination = r² this is the value usually reported to convey the strength of a relationship between two variables
What is an example of primary disease prevention?
Vaccination; a vaccinated person is no longer susceptible to the disease
What is an example of secondary disease prevention?
Pap smear; cervical cancer is detected at an early, treatable stage
What is an example of tertiary disease prevention?
Chemotherapy, which seeks to reduce disability from disease once it has occurred
Define the term primary prevention of disease.
The prevention of disease occurrence
Define the term secondary prevention of disease.
The early detection of disease
Define the term tertiary prevention of disease.
The prevention or reduction of disability from disease
Name three services that can be provided as important preventive measures for patients with diabetes.
Eye exams, foot exams, and urine tests for protein
Name three services that can be provided as important preventative measures for patients who use drugs.
Hepatitis immunizations, HIV tests, and tuberculosis tests
Name three services that can be provided as important preventive measures for patients with alcoholism.
Influenza immunizations, pneumococcal immunizations, and tuberculosis tests
Name a service that can be provided as an important preventive measure for patients who are overweight.
Blood sugar tests for diabetes
Name a service that can be provided as an important preventive measure for patients who are homeless, inmates, or recent immigrants.
Tuberculosis tests
Name five services that can be provided as important preventive measures for patients who exhibit high-risk sexual behavior.
HIV, hepatitis B, syphilis, gonorrhea, and chlamydia tests
What infectious diseases are reportable in all states?
“Hep, Hep, Hooray, the SSSMMART Chick is Gone”: Hepatitis A, Hepatitis B, Hepatitis C, HIV, Salmonella, Shigella, Syphilis, Measles, Mumps, AIDS, Rubella, Tuberculosis, Chicken pox, and Gonorrhea
Name the twelve diseases that are reportable in all states.
AIDS, chickenpox, gonorrhea, hepatitis A and B, measles, mumps, rubella, salmonella, shigella, syphilis, and TB
True or False? HIV infection is reportable only in some states.
TRUE
In order (from most common to least common) what are the five leading causes of death of infants?
Congenital anomalies, short gestation/low birth weight, sudden infant death syndrome, maternal complications of pregnancy, and respiratory distress syndrome
In order (from most common to least common) what are the five leading causes of death of children who are between the ages of 1 and 14 years?
Injuries, cancer, congenital anomalies, homicide, and heart disease
In order (from most common to least common) what are the five leading causes of death of people who are between the ages of 15 and 24 years?
Injuries, homicide, suicide, cancer, and heart disease
In order (from most common to least common) what are the five leading causes of death of people who are between the ages of 25 and 64 years?
Cancer, heart disease, injuries, suicide, and stroke
In order (from most common to least common) what are the six leading causes of death of people who are older than 65?
Heart disease, cancer, stroke, COPD, pneumonia, and influenza
Healthcare payment are federal programs that originated from amendments to what act?
The Social Security Act
What are the names of two federally funded healthcare programs that originated from amendments to the Social Security Act?
Medicare and Medicaid
What part of Medicare covers hospital-related costs?
Medicare Part A
What part of Medicare covers doctor bills?
Medicare Part B
What patient population is eligible for Medicare?
Elderly patients (MedicarE is for the Elderly.)
What patient population is eligible for Medicaid?
Low-income/destitute patients (MedicaiD is for the Destitute)
True or False? Medicaid is federal and state assistance for individuals with very low incomes.
TRUE
What program offers matching state and federal government funding for children’s healthcare coverage?
CHIP (Children’s Health Insurance Program)
What is the role of third-party payers in the American healthcare system?
These are insurance companies that collect money from large populations to pay all or a portion of the medical bills of current patients
In a fee-for-service system, how are physicians paid?
Physicians are paid for each procedure
In a capitation system, how are physicians paid?
Physicians are paid for a period of time, independent of procedures performed
