CPH EXAM 499 Questions with Verified Answers
Attributable risk - CORRECT ANSWER Rate of disease in exposed individuals that can be attributed to the
... [Show More] exposure. Or the proportion of all cases that can be attributed to a particular exposure.
Adjusted rate - CORRECT ANSWER Effects of differences in composition of pops being compared have been minimized by statistical methods.
ex: regression analysis and strandardization
-often used on rates or relative risks
Ecological Fallacy - CORRECT ANSWER Bias that may occur because an association observed between variables or an aggregate level does not represent the association that exists at an individual level
Confidence Interval - CORRECT ANSWER 95% confident that the true value of a variable is contained within the interval.
-used to account for sampling variability
-it is a point estimate +_ margin of error, where the point estimate is the best estimate of teh unknown parameter and the margin of error is the product of the confidence level and the standard error.
if a 95% CI for the differences in mean does not include 0 (the null value) then there is eveidence of a statistically significant difference at sigma=0.05
Clinical Trial Phases - CORRECT ANSWER 1. Safety and Pharmacologic profiles
2. pilot efficacy studies
3. extensive clinical trials
4. after the FDA approves, look at specific effects to establish incidence of adverse reactions, etc. longterm use effects.
interpretation of studies - CORRECT ANSWER temporality: cause precedes effect
Specificity: important in assessing the possibility of biases.
Consistency: several studies showing similar results. homogeneity statistically.
Confounders - CORRECT ANSWER -non-causal association between exposure and outcome as a result of a third variable.
-distortion of effect by other factors
-must be related to exposure AND outcome
-not an intermediate variable on causal pathway
Controlling for confounders - CORRECT ANSWER before data collection: random collection, individual matching, frequency matching
After data collection: direct adjustment, indirect adjustment, mantel-haenszel, regression techniques
Quality Assurance vs. Quality Control - CORRECT ANSWER QA: ensure quality before data collection
QC: monitor and maintain quality during study
reliability vs. validity - CORRECT ANSWER R: precision, reproducibility
V: accuracy, absence of bias
systematic error - CORRECT ANSWER (lack of validity) if there's a difference between what is actually being estimated and what is intended to be measured. Increasing sample size doesn't help.
Random Error - CORRECT ANSWER (lack of precision) occurs, but increasing sample size helps.
RCT studies - CORRECT ANSWER Tests efficacy or effectiveness of healthcare services. random allocation of participants to different treatments. Includes blinding, placebo. gold standard for evidence.
Community Intervention/cluster RCT - CORRECT ANSWER community-wide basis or groupwide
Case-Crossover RCT design - CORRECT ANSWER -cases serve as their own control
-exposure has transient effect
Cross Sectional Studies - CORRECT ANSWER SNAPSHOT! at a single point in time. tells the prevalence and association. causation cannot be implied. a study that examines the relationship between diseases and other variables as they exist in a defined population at one particular time.
Matching - CORRECT ANSWER used to make cases and controls as similar as possible to avoid confounding. ex: race, gender, age. +Maybe the only way to control confounding. increases statistical power, straightforward. -requires use of special analytical techniques, residual confounding can occur if you match continuous variables by category.
types of matching - CORRECT ANSWER individual matching: case and control matched individually
frequency matching: a group of controls
Minimum Euclidean Distance measure: match to closest person.
Cohort Studies - CORRECT ANSWER RISK RATIO, RELATIVE RISK, INCIDENCE RATE, RATE RATIO
-rare exposures
-group of subjects who shared experiences during a particular time. Determines if incidence is related to exposure.
Concurrent/longitudinal cohort studies - CORRECT ANSWER starts now (with a baseline exam) and goes into future. expensive and time intensive.
non-concurrent/retrospective cohort studies - CORRECT ANSWER assembled in past based on existing records. faster and quicker, but records can be limited or biased. follow up can be hard.
Prevalence of disease - CORRECT ANSWER measure of the burden of disease in a community (new and existing cases). the number of events in a given population at a designated time.
-obscures causal relationships
point prevalence - CORRECT ANSWER -proportion of pop that is diseased during a single point of time.
-at a specific point in time
number of cases at a particular moment/
number in population at that moment
period prevalence - CORRECT ANSWER -proportion of pop that is diseased during a specified duration of time.
-during a specific period of time
number of cases during a specified time period/
number in population at midpoint of period
incidence of disease - CORRECT ANSWER measure of risk (new cases)
the rate at which people without a disease develop the disease during a specific period of time.
#of new cases over a period of time/
population @ risk of the disease in that time
incidence rate (also incidence density) - CORRECT ANSWER CASES OF DISEASE/PERSON-TIME AT RISK
TIME is important.
-it shows greater accuracy, but is hard to calculate.
-used for causal research
Incidence Proportion - CORRECT ANSWER CASES OF DISEASE/PERSONS AT RISK
cumulative risk/average risk
the proportion of a group of people who experience the onset of a health-related event during a specified time interval.
Incidence Odds - CORRECT ANSWER CASES OF DISEASE/SURVIVORS
Ratio of people who experience outcome to ratio of people who no not experience outcome.
Rate Ratio - CORRECT ANSWER ratio of incidence rate in the exposed group to the non-exposed group
Risk Ratio - CORRECT ANSWER -measures the increased risk for developing a disease after being exposed to a risk factor compared to not being exposed to the risk factor.
RR= risk for the exposed/
risk for the unexposed
-often referred to as "relative risk"
Odds Ratio - CORRECT ANSWER Ratio of incidence odds in exposed group to non-exposed group.
[p1/(1/p1)]/[p2/(1/p2)]
OR: a*d/b*c
exposed not exposed
cases a b
controls c d
Information Bias (also observational bias) - CORRECT ANSWER systematic error/flaw due to incorrect definition, measurement, or classification that results in reduced quality (accuracy)
Ex: false positives/negatives or errors in death records.
Differential Information Bias - CORRECT ANSWER Probability of cases vs. non-cases of misclassification is different.
Non-Differential Information Bias - CORRECT ANSWER Probability of cases vs. non-cases of misclassification is NOT different.
Selection Bias - CORRECT ANSWER When sample/participants aren't representative. how to avoid: control confounders and choose good comparison group.
power - CORRECT ANSWER -the ability to reject the null hypothesis when the null is in fact false.
-probability of detecting a difference if one truly exists. 1-beta= probability of declaring a difference not statistically significant when a difference truly exists.
Type 1 Error - CORRECT ANSWER reject the null hypothesis when it is true
alpha or
Type 11 Error - CORRECT ANSWER fail to reject the null hypothesis when it is false
beta
aggregate data - CORRECT ANSWER vital stats, data from govt databases, summaries from reporting systems, production and sales data, group-level. COMBINED
individual level data - CORRECT ANSWER questionnaires, medical records, national surveys, biological specimens
Stages of disease prevention - CORRECT ANSWER Primary, secondary, tertiary
Primary Disease Prevention - CORRECT ANSWER Prevent it from occurring (vaccines)
Secondary Disease Prevention - CORRECT ANSWER Modify severity (better access to ER)
Tertiary Disease Prevention - CORRECT ANSWER Rehabilitation. measures to prevent reoccurrence of disease
Rate of Disease - CORRECT ANSWER how fast is the disease occurring in the population
Proportion of Disease - CORRECT ANSWER What fraction of the population is affected?
Case Fatality (CF) or Fatality Rate - CORRECT ANSWER Measures of the severity of disease.
9 deaths per 10,000/1 year
Within a given year, out of 10,000 people diagnosed with a disease, 9 died.
Secondary Attack Rate (person-to-person spread) - CORRECT ANSWER # of persons sick by the primary case/# exposed to primary case
Attack Rate - CORRECT ANSWER # of people at risk who develop disease /# of people at risk
Outbreak investigation steps - CORRECT ANSWER 1. define epidemic
2. look for the time-place interaction of cases
3. look for combination of variables
4. Develop hypothesis
5. Recommend control measures
Common Source Outbreaks - CORRECT ANSWER groups of persons exposed to common agent
Propagated Outbreaks - CORRECT ANSWER spreads gradually from person to person
Mixed epidemic Outbreaks - CORRECT ANSWER both common source and person to person exposure
Persistent Organic Pollutants (POPs) - CORRECT ANSWER toxic chemicals that persist in the environment for long periods of time. adverse effects on humans and animals. circulates globally.
organophosphates - CORRECT ANSWER pesticides that contain phosphorus. short lived. toxic when first applied.
Mutagen - CORRECT ANSWER agent that causes a permanent genetic change outside of normal growth.
mutagenicity - CORRECT ANSWER capacity to cause permanent genetic change
MRSA - CORRECT ANSWER bacterial strains. resistent to antibiotics. benign colonizers of the skin. may cause severe infections.
Morbidity - CORRECT ANSWER rate of disease, incidence. HOW MANY PEOPLE ARE SICK
Mortality - CORRECT ANSWER death rate. PEOPLE WHO HAVE DIED.
Metabolism - CORRECT ANSWER conversion or breakdown of a substance from one form to another by a living organism
metabolites - CORRECT ANSWER substance produced by biological processes
metabolomics - CORRECT ANSWER use of genomic information to facilitate studies of metabolic processes.
Latency - CORRECT ANSWER time from 1st exposure until the appearence of a toxic effect.
IRIS (integrated risk information system) - CORRECT ANSWER descriptive, quantitative regulatory information on chemicals. health professionals not experts.
Incidence - CORRECT ANSWER # of new cases in a defined population over a specific time period.
hydrophilic - CORRECT ANSWER strong affinity for water
hydrophobic - CORRECT ANSWER strong aversion for water
helminths - CORRECT ANSWER group of parasites that infect humans (Schistosoma haematobium) cestodes: beef and pork tapeworms
HACCP (hazard analysis and critical control points) - CORRECT ANSWER production control system for the food industry. identifies potential contamination and then strictly manages and monitors points. designed to *prevent* rather than catch.
gray (Gy) - CORRECT ANSWER international system unit of absorbed dose
exposure-dose reconstruction - CORRECT ANSWER method of estimating the amount of past exposures to hazardous substances. computers and approximation methods can be used when info is missing or limited.
EPCRA (emergency planning and community right-to-know act) - CORRECT ANSWER requirements for federal, stat and local govts regarding emergency planning and CRTK reporting on hazardous and toxic chemicals.
-triggered by Bhopal, India 2,000 people died by release of methyl isocyanate.
ED50 - CORRECT ANSWER dose of drug that is pharmacologically effective for 50% of the population.
disease vector - CORRECT ANSWER intermediate host for parasites. required for development. delivers parasite to subsequent hosts.
ex: schistosoma
Curie - CORRECT ANSWER basic unit to describe the intensity of radioactivity in a sample of material.
cryptosporidium - CORRECT ANSWER microbe that is transmitted through water and person-to-person contact. causes acute diarrhea, stomach pain, vomiting, fever.
-milwaukee episode, largest waterborne disease outbreak.
Criteria Pollutants - CORRECT ANSWER 1970 ammendment to Clean Air Act. required EPA to set standards for 6 pollutants.
ozone, carbon monoxide, total suspended particles, sulfurdioxide, lead, nitrogenoxide.
Comparison value - CORRECT ANSWER the calculated concentration of a substance in air, food, or soil that is unlikely to cause harm. used as a screening level during assessment process.
Command and Control - CORRECT ANSWER regulates how activities need to be carried out. compliance monitoring and sanctions of trespasses. CONS: inflexibility, not adaptable, no incentive for reaching higher.
CBRNE incidents - CORRECT ANSWER deliberate malicious acts with the intention of killing others and disrupting society.
CHEMICAL, BIOLOGICAL, RADIOACTIVE, NUCLEAR, EXPLOSIVE.
Temporality - CORRECT ANSWER The cause must precede the effect
Specificity - CORRECT ANSWER -the proportion of truly nondiseased persons who are so identified by the screening test.
-Specificity of the effect is important in assessing possibility of biases
true negatives/disease free population
D/B+D
"of those who do not have disease, __% will test negative."
Interaction - CORRECT ANSWER This occurs when the incidence of disease in the presence of two or more risk factors differs from the incidence expected to result from their individual effects
Epidemiology's basic ethical principles - CORRECT ANSWER 1. respect for people
2. Beneficence (do not harm)
3. Justice
Applications of Epidemiology's basic ethical principles - CORRECT ANSWER 1. informed consent
2. assessment of risk and benefit
3. selection of subjects
Tuskegee Syphilis Experiment - CORRECT ANSWER A clinical study conducted between 1932 and 1972 in Tuskegee, Alabama by The U.S. Public Health Service. 399 impoverished African American sharecroppers with syphilis were recruited for research related to the natural progression of the untreated disease. After penicillin was discovered as a cure, researchers continued to deny such treatments to medical participants for another 25 years. Many patients were lied to and given placebo treatments so researchers could observe the progression of the fatal disease. This study led to the 1979 Belmont Report and establishment of the *Office for Human Research Protection (OHRP).* In 1974, Congress passed the National Research Act and created a commission to study and write regulations governing studies involving human participants.
Accuracy - CORRECT ANSWER The degree to which a measurement or an estimate based on measurements represents the true value of the attribute that is being measured.
Acute Disease - CORRECT ANSWER a health effect with sudden onset, often brief. sometimes used to mean severe.
adjusted rate - CORRECT ANSWER a rate in which the effects of differences in composition of the populations being compared have been minimized by statistical measures.
Association - CORRECT ANSWER statistical dependence between two or more events, characteristics or other variables.
attack rate - CORRECT ANSWER the cumulative incidence of infection in a group observed over a period during an epidemic.
Crude rate - CORRECT ANSWER a summary rate based on the actual number of events in a population over a given time period.
death rate - CORRECT ANSWER an estimate of the portion of a population that dies during a specific period.
#of people dying /population
Ecologic study - CORRECT ANSWER a study in which the units of analysis are populations or groups of people rather than individuals.
etiology - CORRECT ANSWER the science of causes, causality.
Hawthorne Effect - CORRECT ANSWER The effect of knowing that you're being studied influences behavior.
healthy worker effect - CORRECT ANSWER workers usually exhibit lower overall death rates than the general population because chronically ill are bared from employment.
index case - CORRECT ANSWER the first case in a family or other defined group to come to the attention of the investigator
induction period - CORRECT ANSWER the period required for a specific cause to produce disease. the interval from the causal action of a factor to the initiation of the disease.
internal validity - CORRECT ANSWER the index and comparison groups are selected and compared in such a manner that the observed differences between them can be attributed only to the hypothesized effect under investigation.
lead time bias - CORRECT ANSWER overestimation of survival time, due to the backward shift in the starting point for measuring survival that arises when diseases are detected early (screening procedures).
length bias - CORRECT ANSWER a systematic error due to selection of disproportionate numbers of long-duration cases.
measurement error - CORRECT ANSWER a mismatch between an estimated value and its true value.
natality - CORRECT ANSWER the occurrence of births in a population
person-time - CORRECT ANSWER a measurement combining persons and time as the denominator in incidence and mortality rates when, for varying periods, individual subjects are at risk of developing disease or dying.
predictive value - CORRECT ANSWER the probability that a person with a positive test is truly positive. or the probability that a person who tests negative is actually negative.
probability sample - CORRECT ANSWER all individuals have an equal chance of selection.
proportional mortality ratio - CORRECT ANSWER the proportion of observed deaths from a specified condition in a defined population, divided by the proportion of deaths expected from the condition in a standard population. expressed on an age-specific basis or after age adjustment.
p-value - CORRECT ANSWER the probability that a test statistic would be as extreme as or more extreme than observed if the null hypothesis were true.
small p-value <.05 leads to rejection of the null hypothesis. the result is statistically significant.
large p-value >.05 leads to fail to reject the null hypothesis. there was no effect.
quasi-experimental study - CORRECT ANSWER investigator lacks full control over allocation or timing, but conducts the study as if it were an experiment.
relative risk - CORRECT ANSWER -measure of the association between exposure to a particular factor and risk of a cetain outcome.
-doesn't measure probability that someone with the factor will develop the disease
incidence rate among exposed/
incidence rate among nonexposed
sensitivity - CORRECT ANSWER the proportion of truly diseased persons in the screened population who are identified as diseased by the screening test.
"of those who have the disease, __% will test positive"
disease not diseased total
positive a b a+b
negative c d c+d
total a+c b+d a+b+c+d
a= true positives
b= false positives
c=false negatives
d=true negatives
sensitivity = a/(a+c)
specificity= d/(b+d)
predictive value (positive test result) a/(a+b)
predictive value (negative test result) d/(c+d)3
standardized mortality ratio - CORRECT ANSWER the ratio of the number of deaths observed in the study group or population to the number that would be expected if the study population had the same specific rates as the standard population x100. usually a percentage.
temporality - CORRECT ANSWER the timing of information about cause and effect.
Validity - CORRECT ANSWER measurement: does it measure what it says it does?
study: the degree to which the inferences drawn from the study are warranted.
vital statistics - CORRECT ANSWER systematically tabulated information on deaths, births, marriages, etc.
proportionate mortality ratio - CORRECT ANSWER calculated as the number of deaths within a population due to a specific disease or cause divided by the total number of deaths in the population.
Case Control Study - CORRECT ANSWER ODDS RATIO
-no incidence data
-nested CC: inside of a cohort study
-rare diseases, outbreak studies
-looks at 1 outcome and infinite exposures
-good when little is known about disease
-cheap and fast
-difficult to infer temporal relationship between exposure and disease
Eras of Public Health - CORRECT ANSWER 1. battling epidemics (before 1850)
2. building state and local infrastructure
3. filling gaps in medical care delivery
4. preparing for and responding to community health threats.
Biochemical oxygen demand (BOD) - CORRECT ANSWER Measure of the amount of oxygen consumed in the biological processes that break down organic matter in water
BOD5 - CORRECT ANSWER amount of oxygen consumed in 5 days by biological processes breaking down organic matter. [Show Less]