Study Guide Exam 3 Flashcards
Reliability vs validity
Reliability refers to the consistency of a measure (whether the results can be reproduced under the same conditions). Validity refers to the accuracy of a measure (whether the results really do represent what they are supposed to measure).
What is random error?
Is another way of saying there is lack of reliability in the study
Why do random errors reflect fluctuations occurring by chance around a true value of a parameter?
Sampling error
Variability in the data itself
Imprecision in measurement
When does sampling error occur?
Brief reminder: epidemiologic studies draw inferences about the experiences of an entire pop based on an eval of only a sample
Occurs when the sample selected is not representative of the source pop for reasons other than systematic bias in the way ppl were recruited.
What can systematic errors be caused by?
Selection bias, information bias, or confounding
Characteristics of lack of internal validity
It’s the same as bias in a study.
It is systematic error.
It is affected by how the study was designed and carried out
Definition of systematic errors?
Errors in how samples were selected or the quality of the data used
What is external validity affected by?
The source population from which the sample is drawn and by the level of internal validity in the study
Definition of selection bias
A bias d/t differences in the manner in which study groups are formed: bias in how people are selected into the sample
Definition of information bias
Results from systematic differences in the way data on exposure or outcome are obtained from the various study groups
It is a bias in terms of the data itself and its ascertainment
Can be introduced as a result of systematic measurement error in assessment of either exposure and/or dz
