CHLH 274 Quiz 6 Study Guide
Questions with Actual Answers 2025-
2026 Updated.
Internal Validity - Answer a study has internal validity if there have been proper selection of
study groups and a lack of error in measurement. Concerned with the appropriate
measurement of exposure, measurement of outcome, and association between exposure and
disease.
External Validity - Answer the ability to generalize beyond a set of observations to some
universal statement.
2 Sources of Error in Epidemiology - Answer Random errors
Systematic errors (bias)
Random Errors - Answer Reflect fluctuations around a true value of a parameter because of
sampling variability.
Caused by= poor precision, sampling error, variability in measurement
Poor Precision - Answer Occurs when the factor being measured is not measured sharply.
Analogous to aiming a rifle at a target that is not in focus.
Precision can be increased by increasing sample size or the number of measurements.
Sampling Error - Answer 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 - Answer The lack of agreement in results from time to time
reflects random error inherent in the type of measurement procedure employed.
Systematic Error (Bias) - Answer Deviation of results or inferences from the truth, or
processes leading to such deviation. Strays away from the truth, unlike random error.
Caused by= selection bias, information bias, confounding
Selection Bias - Answer 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 - Answer Can be introduced as a result of measurement error in assessment
of both exposure and disease.
Types of information bias=
---Recall bias: better recall among cases than among controls.
---Interviewer/abstractor bias--occurs when interviewers probe more thoroughly for an
exposure in a case than in a control.
---Prevarication (lying) bias--occurs when participants have ulterior motives for answering a
question and thus may underestimate or exaggerate an exposure
Confounding - Answer The distortion of the estimate of the effect of an exposure of interest
because it is mixed with the effect of an extraneous factor.
Occurs when the crude and adjusted measures of effect are not equal (difference of at least
10%).
Can be controlled for in the data analysis.
Criteria of Confounders - Answer To be a confounder, an extraneous factor must satisfy the
following criteria=
Be a risk factor for the disease.
Be associated with the exposure.
Not be an intermediate step in the causal path between exposure and disease.
Techniques to Reduce Selection Bias - Answer Develop an explicit (objective) case definition.
Enroll all cases in a defined time and region.
Strive for high participation rates (incentives)
Take precautions to ensure representativeness
Techniques to Reduce Information Bias - Answer Blind interviewers as to subjects' study
status.
Provide standardized training sessions and protocols.
Use standardized data collection forms.
Blind participants as to study goals and classification status.
Screening - Answer the presumptive identification of unrecognized disease or defects by the
application of tests, examinations, or other procedures that can be applied rapidly.
Screening for Diseases - Answer A tenet of public health is that primary prevention of
disease is the best approach
Questions with Actual Answers 2025-
2026 Updated.
Internal Validity - Answer a study has internal validity if there have been proper selection of
study groups and a lack of error in measurement. Concerned with the appropriate
measurement of exposure, measurement of outcome, and association between exposure and
disease.
External Validity - Answer the ability to generalize beyond a set of observations to some
universal statement.
2 Sources of Error in Epidemiology - Answer Random errors
Systematic errors (bias)
Random Errors - Answer Reflect fluctuations around a true value of a parameter because of
sampling variability.
Caused by= poor precision, sampling error, variability in measurement
Poor Precision - Answer Occurs when the factor being measured is not measured sharply.
Analogous to aiming a rifle at a target that is not in focus.
Precision can be increased by increasing sample size or the number of measurements.
Sampling Error - Answer 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 - Answer The lack of agreement in results from time to time
reflects random error inherent in the type of measurement procedure employed.
Systematic Error (Bias) - Answer Deviation of results or inferences from the truth, or
processes leading to such deviation. Strays away from the truth, unlike random error.
Caused by= selection bias, information bias, confounding
Selection Bias - Answer 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 - Answer Can be introduced as a result of measurement error in assessment
of both exposure and disease.
Types of information bias=
---Recall bias: better recall among cases than among controls.
---Interviewer/abstractor bias--occurs when interviewers probe more thoroughly for an
exposure in a case than in a control.
---Prevarication (lying) bias--occurs when participants have ulterior motives for answering a
question and thus may underestimate or exaggerate an exposure
Confounding - Answer The distortion of the estimate of the effect of an exposure of interest
because it is mixed with the effect of an extraneous factor.
Occurs when the crude and adjusted measures of effect are not equal (difference of at least
10%).
Can be controlled for in the data analysis.
Criteria of Confounders - Answer To be a confounder, an extraneous factor must satisfy the
following criteria=
Be a risk factor for the disease.
Be associated with the exposure.
Not be an intermediate step in the causal path between exposure and disease.
Techniques to Reduce Selection Bias - Answer Develop an explicit (objective) case definition.
Enroll all cases in a defined time and region.
Strive for high participation rates (incentives)
Take precautions to ensure representativeness
Techniques to Reduce Information Bias - Answer Blind interviewers as to subjects' study
status.
Provide standardized training sessions and protocols.
Use standardized data collection forms.
Blind participants as to study goals and classification status.
Screening - Answer the presumptive identification of unrecognized disease or defects by the
application of tests, examinations, or other procedures that can be applied rapidly.
Screening for Diseases - Answer A tenet of public health is that primary prevention of
disease is the best approach
