(M) Validity of Epidemiologic Studies

Question 1

try to provide accurate answers to questions

Answer 1

Epidemiological studies

Question 2

T or

Estimates ≠ Real Prevalence or Real Risk → Error

Answer 2

T

Question 3

involves generating and testing hypothesis about factors that cause or prevent disease

Answer 3

Epidemiologic research

Question 4

eliminate alternative explanations for his/her findings

Answer 4

major objective of every investigator who tests an etiologic hypothesis

Question 5

one in which the observed association is not due to various sources of error (systematic and random errors)

Answer 5

valid study

Question 6

from the poor design and/or conduct of the study
* Noncomparability of Groups
* Measurement Flaws

Answer 6

bias from systematic error

Question 7

Underestimate or overestimate the true measure of association

Answer 7

bias from incorrect estimate of the measure of association

Question 8

Results from procedures used to select subjects and factors that influence participation in the study

Answer 8

Selection Bias

Question 9

Selection Bias

Groups being compared should be as similar as possible with respect to all other factors that may be related to the disease except the determinant under investigation

Answer 9

Principle in the Selection of Study Groups

Question 10

Types of Selection Bias

Answer 10

• Sampling Bias
• Allocation Bias
• Responder Bias

Question 11

Systematically excluding or over-representing certain groups

Answer 11

Sampling Bias

Question 12

E.g. A study to estimate the prevalence of smoking in a population, choosing a city center as location for study

Answer 12

Sampling Bias

Question 13

Systematic differences in the way in which subjects are recruited into different groups for a study

Answer 13

Allocation Bias

Question 14

E.g. A study may fail to do random sampling

First 20 patients who arrived at the clinic are allocated to a new treatment
Next 20 patients are allocated to an existing treatment
However, the patients who arrived early may be fitter or wealthier, OR alternatively the doctor may have asked to see the most seriously ill patients first

Answer 14

Allocation Bias

Question 15

Missed responders or non-responders

Answer 15

Responder Bias

Question 16

E.g. A study may send questionnaires to members of the control group. If these subjects are from a different social class to the cases, there may be differences in the proportion of responses that are received.

Answer 16

Responder Bias

Question 17

AKA. measurement error, misclassification bias, observation bias

Answer 17

Information Bias

Question 18

A flaw is measuring exposure or outcome variables that resultes in incorrect information between comparison group

Answer 18

Information Bias

Question 19

Systematic differences in data collection, measurement or classification

Answer 19

Information Bias

Question 20

Types of information bias

Answer 20

• Recall Bias
• Social acceptability
• Recording Bias
• Interview Bias
• Follow-up Bias
• Misclassification Bias

Question 21

People suffering from a disease may have spent more time thinking of possible links between their past behavior and their disease than non-sufferers

Answer 21

Recall Bias

Question 22

Cases may report more exposure to possible hazards

Common in case-control studies

Answer 22

Recall Bias

Question 23

Some subjects may exaggerate or understate their responses, or deny that they engage in embarrassing or undesirable activities

Ex. cheating – they may deny this because it is not socially accepted

Answer 23

Social Acceptability Bias

Question 24

Medical records may contain more information on patients who are “cases”

Answer 24

Recording Bias

Question 25

Interviewers may phrase questions differently for different subjects, or write down their own interpretations of what subjects have said

Question of phrasing is different from each group

Answer 25

Interviewer Bias

Question 26

In studies that follow up at intervals, people from certain groups may tend to be lost to followup, or a disproportionate number of exposed subjects may be lost to follow-up compared with non-exposed subjects

Answer 26

Follow-up Bias

Question 27

Patients may be systematically misclassified as either having disease or exposure

Answer 27

Misclassification Bias

Question 28

E.g older people of lower social class may be less likely to express dissatisfaction with a health-related service

Answer 28

Some groups may give different responses

Question 29

T or F

Investigators may look more closely at exposed patients, to try to find the presence of a disease, or they may be more attentive to certain types of subjects.

Answer 29

True

Question 30

The mixing of effects between the exposure, The disease, and a third variable

Answer 30

Confounding

Question 31

what is the third variable

Answer 31

Confounder

Question 32

When present, the association between exposure and disease is distorted

Answer 32

The “third variable problem”

confounder

Question 33

Have an effect on the independent variable, and have big effect on disease

Answer 33

The “third variable problem”

confounder

Question 34

Occurs when a separate factor (or factors) influences the risk of developing a disease, other than the risk factor being studied.

Answer 34

Confounding (confounder)

Question 35

the factor has to be related to the exposure, and it also has to be an independent risk factor for the disease being studied.

Answer 35

To be a confounder

Question 36

common causes of confounding.

Answer 36

Age and Sex

wow naol

Question 37

Confounding =

Answer 37

Spuriousness

(not genuine or authentic )

Question 38

if u see this card

Answer 38

go over the example of confounding

Question 39

T or F

Majority of study is PERFECTLY VALID

Answer 39

F - no study dumbass

Question 40

fators that contributes to study why there is no perfectly valid

Answer 40

• Residual confounding
• Unpredictable nature of chance
• Complexity of bias

Question 41

Eliminate Effect of Confounding in Studies

Answer 41

• Randomization
• Matching
• Stratified analysis

Question 42

ensuring that samples are randomly selected

Answer 42

Randomization

Question 43

In Case-Control study, controls are matched to cases at the start of the study according to particular characteristics which are known to be present in cases (e.g. age, sex, ethnic group, smoking, etc)

Answer 43

Matching

Question 44

dividing subjects into groups at the analysis stage (e.g. by sex, age group, smoker/non-smoker) and analyzing on this basis.

Answer 44

Stratified Analysis

Question 45

if u see this card

Answer 45

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