CHLH 274 Final Exam Questions and Answers Solved Correctly
Internal Validity - Answers when a study has proper selection of study groups and lack of error in
measurement
Internal Validity is concerned w/ - Answers measurement of exposure, measurement of outcome, and
association between exposure and disease
External Validity - Answers implies the ability to generalize beyond a set of observations to some
universal statement
Sources of Error in Epidemiologic Research - Answers random errors and systematic errors (bias)
Random Errors - Answers reflect fluctuations around a true value of a parameter because of sampling
variability
Factors Contributing to Random Error - Answers poor precision, sampling error, and variability in
measurement
Poor Precision - Answers Occurs when the factor being measured is not measured sharply; precision can
be increased by increasing sample size or number of measurements
Sampling Error - Answers occurs when the sample selected is not representative of the target
population; increasing the sample size can reduce the likelihood of sampling error
Variability in Measurement - Answers lack of agreement in results from time to time reflects random
error inherent in the type of measurement procedure employed
Systematic Errors (Bias) - Answers deviation of results or inferences from the truth, or processes leading
to such deviation
Factors that Contribute to Systematic Errors - Answers selection bias, information bias, confounding
Selection Bias - Answers arises when the relation between exposure and disease is different for those
who participate and those who theoretically would be eligible for study but do not participate.
Information Bias - Answers can be introduced as a result of measurement error in assessment of both
exposure and disease.
Recall bias (type of information bias) - Answers better recall among cases than among controls
Interviewer/abstractor bias (type of information bias) - Answers occurs when interviewers probe more
thoroughly for an exposure in a case than in a control
Prevarication (lying) bias (type of information bias) - Answers occurs when participants have ulterior
motives for answering a question and thus may underestimate or exaggerate an exposure
, confounding - Answers distortion of the estimate of the effect of an exposure of interest bc it is mixed
with the effect of an extraneous factor; occurs when the crude and adjusted measures of effect are not
equal (difference of 10%); can be controlled for in the data analysis
criteria of confounders - Answers to be a confounder, an extraneous factor must satisfy the following
critera: be a risk factor for the disease, be associated with the exposure, and not be intermediate step in
the casual path between exposure and disease
Techniques to Reduce Selection Bias - Answers develop an explicit (objective) case definition, enroll all
cases in defined time and region, strive for high participation rates (incentives), and take precautions to
ensure representatives
Techniques to Reduce Information Bias - Answers blind interviewers as to subjects' study status, provide
standardized training sessions and protocols, use standardized data collection forms, and blind
participants as to study goals and classification status
Screening for Disease - Answers presumptive identification of unrecognized disease or defects by the
application of tests, examinations, or other procedures that can be applied rapidly; positive results are
followed by diagnostic tests to confirm actual disease
Examples of screening programs that are conducted to screen interested and concerned individuals for
specific health problems - Answers hypertension and cervical cancer
Diagnosis - Answers process of confirming an actual case of a disease
Multiphasic Screening - Answers cost effective approach is to screen for more than one disease; use of
two or more screening tests together among large groups of people
Multiphasic Screening is administered by: - Answers pre-employment physical, passing examination may
be a necessary condition for employment in the organization
Multiphasic Screening serves as a benefit for employment via: - Answers some companies repeat the
screening examination on an annual basis, finding are sent to employee's own physicians while
maintaining confidentiality
Multiphasic Screening programs: - Answers assess risk factor status, individual or family history of
illness, collect physiological and health measurements
Mass Screening (population screening) - Answers screening of total population groups on large scale,
regardless of risk status
Selective Screening (targeted screening) - Answers applied to subsets of the population at high risk for
disease or certain conditions as a result of family history, age, and environmental exposures
population/epidemiologic surveys - Answers purpose is to gain knowledge regarding the distribution and
determinants of disease in selected populations; no benefit to the participant is implied
Internal Validity - Answers when a study has proper selection of study groups and lack of error in
measurement
Internal Validity is concerned w/ - Answers measurement of exposure, measurement of outcome, and
association between exposure and disease
External Validity - Answers implies the ability to generalize beyond a set of observations to some
universal statement
Sources of Error in Epidemiologic Research - Answers random errors and systematic errors (bias)
Random Errors - Answers reflect fluctuations around a true value of a parameter because of sampling
variability
Factors Contributing to Random Error - Answers poor precision, sampling error, and variability in
measurement
Poor Precision - Answers Occurs when the factor being measured is not measured sharply; precision can
be increased by increasing sample size or number of measurements
Sampling Error - Answers occurs when the sample selected is not representative of the target
population; increasing the sample size can reduce the likelihood of sampling error
Variability in Measurement - Answers lack of agreement in results from time to time reflects random
error inherent in the type of measurement procedure employed
Systematic Errors (Bias) - Answers deviation of results or inferences from the truth, or processes leading
to such deviation
Factors that Contribute to Systematic Errors - Answers selection bias, information bias, confounding
Selection Bias - Answers arises when the relation between exposure and disease is different for those
who participate and those who theoretically would be eligible for study but do not participate.
Information Bias - Answers can be introduced as a result of measurement error in assessment of both
exposure and disease.
Recall bias (type of information bias) - Answers better recall among cases than among controls
Interviewer/abstractor bias (type of information bias) - Answers occurs when interviewers probe more
thoroughly for an exposure in a case than in a control
Prevarication (lying) bias (type of information bias) - Answers occurs when participants have ulterior
motives for answering a question and thus may underestimate or exaggerate an exposure
, confounding - Answers distortion of the estimate of the effect of an exposure of interest bc it is mixed
with the effect of an extraneous factor; occurs when the crude and adjusted measures of effect are not
equal (difference of 10%); can be controlled for in the data analysis
criteria of confounders - Answers to be a confounder, an extraneous factor must satisfy the following
critera: be a risk factor for the disease, be associated with the exposure, and not be intermediate step in
the casual path between exposure and disease
Techniques to Reduce Selection Bias - Answers develop an explicit (objective) case definition, enroll all
cases in defined time and region, strive for high participation rates (incentives), and take precautions to
ensure representatives
Techniques to Reduce Information Bias - Answers blind interviewers as to subjects' study status, provide
standardized training sessions and protocols, use standardized data collection forms, and blind
participants as to study goals and classification status
Screening for Disease - Answers presumptive identification of unrecognized disease or defects by the
application of tests, examinations, or other procedures that can be applied rapidly; positive results are
followed by diagnostic tests to confirm actual disease
Examples of screening programs that are conducted to screen interested and concerned individuals for
specific health problems - Answers hypertension and cervical cancer
Diagnosis - Answers process of confirming an actual case of a disease
Multiphasic Screening - Answers cost effective approach is to screen for more than one disease; use of
two or more screening tests together among large groups of people
Multiphasic Screening is administered by: - Answers pre-employment physical, passing examination may
be a necessary condition for employment in the organization
Multiphasic Screening serves as a benefit for employment via: - Answers some companies repeat the
screening examination on an annual basis, finding are sent to employee's own physicians while
maintaining confidentiality
Multiphasic Screening programs: - Answers assess risk factor status, individual or family history of
illness, collect physiological and health measurements
Mass Screening (population screening) - Answers screening of total population groups on large scale,
regardless of risk status
Selective Screening (targeted screening) - Answers applied to subsets of the population at high risk for
disease or certain conditions as a result of family history, age, and environmental exposures
population/epidemiologic surveys - Answers purpose is to gain knowledge regarding the distribution and
determinants of disease in selected populations; no benefit to the participant is implied
