Question

3a. The ability for researchers to generalize the results of their study to the general population is called:

1. Internal validity
2. External validity
3. Response validity
4. Reliability

3b. If a screening test for a fast growing, deadly disease has been producing too many false negatives, which adjustment should you make to the screening tool?

1. Decrease sensitivity
2. Decrease specificity
3. Increase sensitivity
4. Increase specificity

3c. A screening test that (i) does not miss a lot of individuals with the disease, but (ii) inappropriately screens positive many individuals who do not have the disease, could be referred to as

1. High sensitivity/ high specificity
2. Low sensitivity/ low specificity
3. Low sensitivity / high specificity
4. High sensitivity/ low specificity

3d. A case-control study was performed to determine whether head injury was associated with an increased risk of brain tumors in children. Two hundred (200) cases with brain cancer were identified from the state cancer registry, and 200 controls were recruited from the same neighborhoods where the cases lived. The mothers of the children completed a questionnaire that asked them to describe their child’s past history of head injury. The investigators found that the mothers of the children with brain tumors reported a past head injury for 70 of the cases while a past history of head injury was reported in 30 of the controls. What type of bias was likely to have influenced the findings of this study?

1. Observer bias
2. Recall bias
3. Length bias
4. Surveillance bias

Answer 1

Answers :

3a.b External validity

External validity is the extent to which your results can be generalized to other contexts.

It is not internal validity because it is influenced by many factors

It is not reliability because it is performed in a specific period of time or in a defined environment.

It is not response validity because is reporting of symptoms and appropriate motivation on cognitive tasks.

3b. C increase sensitivity

By increasing the sensitivity we can decrease the false negative results.

3c.D high sensitivity/ low specificity

the ability to correctly identify people who have the disease — usually comes at the expense of reduced specificity (meaning more false-positives). Likewise, high specificity — when a test does a good job of ruling out people who don’t have the disease – usually means that the test has lower sensitivity (more false-negatives).

3d. D surveillance bias

Surveillance bias, also known as detection bias, arises when patients in one exposure group have a higher probability of having the study outcome detected, due to increased surveillance, screening or testing of the outcome itself, or an associated symptom.