CHLH 274 Final Exam 2025

Internal Validity - -when a study has proper selection of study groups and lack of error in measurement Internal Validity is concerned w/ - -measurement of exposure, measurement of outcome, and association between exposure and disease External Validity - -implies the ability to generalize beyond a set of observations to some universal statement Sources of Error in Epidemiologic Research - -random errors and systematic errors (bias) Random Errors - -reflect fluctuations around a true value of a parameter because of sampling variability Factors Contributing to Random Error - -poor precision, sampling error, and variability in measurement Poor Precision - -Occurs when the factor being measured is not measured sharply; precision can be increased by increasing sample size or number of measurements Sampling Error - -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 - -lack of agreement in results from time to time reflects random error inherent in the type of measurement procedure employed Systematic Errors (Bias) - -deviation of results or inferences from the truth, or processes leading to such deviation Factors that Contribute to Systematic Errors - -selection bias, information bias, confounding Selection Bias - -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 - -can be introduced as a result of measurement error in assessment of both exposure and disease. Recall bias (type of information bias) - -better recall among cases than among controls CHLH 274 CHLH 274 Interviewer/abstractor bias (type of information bias) - -occurs when interviewers probe more thoroughly for an exposure in a case than in a control Prevarication (lying) bias (type of information bias) - -occurs when participants have ulterior motives for answering a question and thus may underestimate or exaggerate an exposure confounding - -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 - -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 - -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 - -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 - -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 - -hypertension and cervical cancer Diagnosis - -process of confirming an actual case of a disease Multiphasic Screening - -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: - -pre-employment physical, passing examination may be a necessary condition for employment in the organization Multiphasic Screening serves as a benefit for employment via: - -some companies repeat the screening examination on an annual basis, finding are sent to employee's own physicians while maintaining confidentiality Multiphasic Screening programs: - -assess risk factor status, individual or family history of illness, collect physiological and health measurements CHLH 274 CHLH 274 Mass Screening (population screening) - -screening of total population groups on large scale, regardless of risk status Selective Screening (targeted screening) - -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 - -purpose is to gain knowledge regarding the distribution and determinants of disease in selected populations; no benefit to the participant is implied epidemiologic surveillance - -aims at the protection of community health through case detection and intervention; continuous observation of the trend