23. SYSTEMATIC ERRORS Flashcards
- What are the two main types of bias in Research?
- Selection Bias
- Information Bias
- What is Selection Bias?
- Systematic Errors arise from the mistakes that are
conducted during the SELECTION of the study sample
- What is Information Bias?
- Systematic Errors arise from the mistakes conducted
during the measurement of the key study variables
KEY STUDY VARIABLES:
- Exposure
- Outcome
- What leads to the rise in Information Bias?
- wrong and inaccurate assessments of either the:
- exposure variables
- or the outcome variables
THESE KINDS OF MISTAKES CAN ARISE EITHER:
- unintentionally from the researcher’s part
- intentionally or unintentionally from the participant’s
part
- What is Instrument Bias?
- this is when the instrument is faulty
- this is an error on the Researcher’s Part
- What is the title we give to any Information bias that arises from the Researcher’s Actions?
- Assessor Bias
- What are the 5 types of Assessor Bias?
- A WRONG AND INACCURATE DIAGNOSIS
- this is due to a Clinical Error
- WHEN THE RESEARCHERS ARE NOT “BLINDED”
- they are aware of the exposure or outcome status of
the participants
- they are aware of the exposure or outcome status of
- WRONG AND INACCURATE MEASUREMENTS
- can be a result of faulty instruments and machines
- WRONG AND INACCURATE MEASUREMENTS
- can be due to poor training of the assessor - MISTAKES CAN HAPPEN DURING
- the recording of the data
- and the transferring of the data from paper into
electrical form
- What is the title we give to any Information bias that arises from the Participant’s Actions?
- Misreporting
- it is mostly called Response Bias
- What are the 5 types of Misreporting Bias?
- WRONG AND INACCURATE ANSWERS
- from the participants
- this is due to the misinterpretation of the question - WRONG AND INACCURATE ANSWERS
- from the participants
- this is due to a sensitive issue relating to the question - WRONG AND INACCURATE ANSWERS
- from the participants
- this is due to poor recall
- this is known as Recall Bias - WRONG AND INACCURATE ANSWERS
- can come from the participants intentionally
- What are the 6 types of Information Bias?
- Recall Bias
- Interviewer Bias
- Observer Bias
- Hawthorne Effect
- Surveillance Bias
- Misclassification Bias
- What is Recall Bias?
THERE ARE PARTICIPANTS THAT HAVE:
- a particular outcome or exposure
- they may remember events more clearly
- this may amplify their recollections
- In which cases is Recall Bias very common?
- it is very common in case-control studies
- What leads to the Primary Differences that are seen in Recall Bias?
THE PRIMARY DIFFERENCE ARISES MORE FROM:
- under-reporting of exposures in the control group
- rather than from over reporting in the case group
- What is Interviewer Bias?
A RESEARCHER’S KNOWLEDGE MAY INFLUENCE:
- the structure of the questions
- and the manner of presentation
THIS COULD INFLUENCE THE RESPONSES FROM THE INDIVIDUALS:
- this is applicable to any study design
- this is especially true if the interviewer is not blinded
to the exposures of the individuals
- What is Observer Bias?
THE RESEARCHERS
- may have preconceived expectations of what they
should find in the examination
THIS IS ESPECIALLY TRUE:
- if they are not blinded to exposures or medical history
- What is the Hawthorne Effect?
- the participants will act differently if they know that
they are being watched
- What is the Surveillance Bias?
- the group with the known exposure or outcome may
be followed more closely - this group can be followed longer than the comparison
group - this is an example of Researcher’s Bias
- What is the Misclassification Bias?
THESE ARE THE ERRORS THAT ARE MADE:
- in either classifying the disease
- or in classifying the exposure status (instrument)
- The errors in which fields of Research can lead to Misclassification Bias?
MEASUREMENT ERRORS IN THE ASCERTAINMENT OF:
- exposure
- outcomes (diseases)
- covariates (cofounders)
- List some examples of Misclassification Biases?
- using cases that are incorrectly classified as controls
- the controls are incorrectly classified as cases
- the exposed groups are incorrectly classified as the
non-exposed groups - the non-exposed groups are incorrectly classified as
the exposed groups
- What are four ways to minimise Bias in Research?
- BE PURPOSEFUL IN THE STUDY DESIGN
- this minimises the chance for bias
- EG: using more than one control group - DEFINE A PRIORITY
- define who is considered to be a case
- define what constitutes to an exposure
- ensure that there is no overlap - DEFINE THE CATEGORIES WITHIN THE GROUPS
CLEARLY- such as age groups
- collections of person years
- such as age groups
- SET UP STRUCT GUIDELINES FOR DATA COLLECTION
- Define methods in which we can set up strict guidelines for Data Collection.
- the observers should be trained to obtain data in the
same fashion - the interviewers should be trained to obtain data in the
same fashion - use more than one observer or interviewer
- do not use too many observers or interviewers
- this would make it difficult to train them all in an
identical manner - Optimise the questionnaire