Epidemiology and Biostatistics 6300
questions and answers with solutions
2025
Absolute differences in risk - ANSWER Risk (control)- Risk (treatment)
Adjusted Rates - ANSWER fictitious rates that are constructed to compare groups that differ by
some important factor. (also known as standardized rates) Direct adjustment uses standard
population age distribution. Indirect adjustment uses standard population age-specific mortality
rates.
- a summarizing procedure
-effects of differences in the composition of populations being compared have been minimized
statistically.
Agent - ANSWER The cause of the disease (i.e. infectious agents, chemical agents, physical
agents).
Alternative hypothesis - ANSWER The hypothesis that a real (true) difference exists between
means or proportions of groups being compared, or that there is a real association between two
variables.
Analytic epidemiology - ANSWER Analytic- study natural history and etiology; discover reasons
for differences in groups; evaluate interventions, treatments, modes of healthcare delivery
(how, why?)
ANOVA - ANSWER (Analysis of Variance)- Method of significance testing based on the ratio of
between-groups variance to within-groups variance. This method is used in statistical analysis if
,the dependent variable is continuous and the independent variable or variables are all
categorical.
Association - ANSWER
Attack Rate - ANSWER Proportion of exposed persons who become ill; the customary measure
used to establish severity of disease outbreak.
Attributable Risk - ANSWER Of the total risk for a particular outcome, AR is the proportion
attributable to a particular exposure. (see risk difference)
Bias - ANSWER Introduction of error that produces deviations or distortions of data that are
predominantly in one direction, as opposed to random error.
Bivariable - ANSWER two variable
Bivariate - ANSWER involving or depending upon two variables
Blinding (masking) - ANSWER Reduces differential misclassification and avoids overestimation of
therapeutic benefit
Case fatality rate - ANSWER Proportion of clinically ill persons who die of the condition under
the study; a marker of virulence.
Case-control study - ANSWER Study groups are defined on the basis of disease (or outcome)
status. The frequency of the risk factor (exposure) in the cases (diseased persons) is compared
with the frequency of the risk factor (exposure) in the controls (nondiseased persons).
, Chi-squared test - ANSWER Statistical significance test used to analyze nominal or dichotomous
data in a contingency table. The first step is to determine that chi-square value for each cell in
the table, by calculating the square of the observed count (0) minus the expected count (E) in a
cell and dividing the result by the expected count for that cell. The next step is to add the values
for all cells in the table. The standard chi-square formula is E[(O-E)2/E]
used for categories NOT continuous data (no mean or SD)
Clinical trial - ANSWER
Cohort study - ANSWER Study in which a clearly identified group is characterized by exposure
and is followed for the outcome.
Confounding variable - ANSWER a confounder (also confounding variable or confounding factor)
is a variable that influences both the dependent variable and independent variable causing a
spurious association.
Correlation - ANSWER Pearson's r- used for continuous, interval or ratio data; Spearman's r-
used in dichotomous, nominal or ordinal data
Cross-sectional study - ANSWER
Crude rates - ANSWER computed using actual numbers of events in a total population over a
given time divided by the total population size--ignores distribution of age.
Descriptive epidemiology - ANSWER Descriptive- person, place, time; determine extent of
disease in community; provide basis for developing public policy and decisions (who, where,
when?)
Direct transmission - ANSWER
questions and answers with solutions
2025
Absolute differences in risk - ANSWER Risk (control)- Risk (treatment)
Adjusted Rates - ANSWER fictitious rates that are constructed to compare groups that differ by
some important factor. (also known as standardized rates) Direct adjustment uses standard
population age distribution. Indirect adjustment uses standard population age-specific mortality
rates.
- a summarizing procedure
-effects of differences in the composition of populations being compared have been minimized
statistically.
Agent - ANSWER The cause of the disease (i.e. infectious agents, chemical agents, physical
agents).
Alternative hypothesis - ANSWER The hypothesis that a real (true) difference exists between
means or proportions of groups being compared, or that there is a real association between two
variables.
Analytic epidemiology - ANSWER Analytic- study natural history and etiology; discover reasons
for differences in groups; evaluate interventions, treatments, modes of healthcare delivery
(how, why?)
ANOVA - ANSWER (Analysis of Variance)- Method of significance testing based on the ratio of
between-groups variance to within-groups variance. This method is used in statistical analysis if
,the dependent variable is continuous and the independent variable or variables are all
categorical.
Association - ANSWER
Attack Rate - ANSWER Proportion of exposed persons who become ill; the customary measure
used to establish severity of disease outbreak.
Attributable Risk - ANSWER Of the total risk for a particular outcome, AR is the proportion
attributable to a particular exposure. (see risk difference)
Bias - ANSWER Introduction of error that produces deviations or distortions of data that are
predominantly in one direction, as opposed to random error.
Bivariable - ANSWER two variable
Bivariate - ANSWER involving or depending upon two variables
Blinding (masking) - ANSWER Reduces differential misclassification and avoids overestimation of
therapeutic benefit
Case fatality rate - ANSWER Proportion of clinically ill persons who die of the condition under
the study; a marker of virulence.
Case-control study - ANSWER Study groups are defined on the basis of disease (or outcome)
status. The frequency of the risk factor (exposure) in the cases (diseased persons) is compared
with the frequency of the risk factor (exposure) in the controls (nondiseased persons).
, Chi-squared test - ANSWER Statistical significance test used to analyze nominal or dichotomous
data in a contingency table. The first step is to determine that chi-square value for each cell in
the table, by calculating the square of the observed count (0) minus the expected count (E) in a
cell and dividing the result by the expected count for that cell. The next step is to add the values
for all cells in the table. The standard chi-square formula is E[(O-E)2/E]
used for categories NOT continuous data (no mean or SD)
Clinical trial - ANSWER
Cohort study - ANSWER Study in which a clearly identified group is characterized by exposure
and is followed for the outcome.
Confounding variable - ANSWER a confounder (also confounding variable or confounding factor)
is a variable that influences both the dependent variable and independent variable causing a
spurious association.
Correlation - ANSWER Pearson's r- used for continuous, interval or ratio data; Spearman's r-
used in dichotomous, nominal or ordinal data
Cross-sectional study - ANSWER
Crude rates - ANSWER computed using actual numbers of events in a total population over a
given time divided by the total population size--ignores distribution of age.
Descriptive epidemiology - ANSWER Descriptive- person, place, time; determine extent of
disease in community; provide basis for developing public policy and decisions (who, where,
when?)
Direct transmission - ANSWER
