CPH EXAM Definitions
Attributable risk - correct answer ✔✔Rate of disease in exposed individuals that can be attributed to the
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 standardization
-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.
Attributable risk - correct answer ✔✔Rate of disease in exposed individuals that can be attributed to the
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 standardization
-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.
