Part 4

Question 1

How do you calculate a + post test probability?

Answer 1

Pretest prob x LR+

Question 2

How do you calculate a - post test probability?

Answer 2

Pretest prob x LR-

Question 3

What is the ability of an experiment to show that the explanatory variables actually caused the observed changes in the outcome variables?

Answer 3

Internal Validity

Question 4

What are the threats to internal validity?

Answer 4

History 
Reliability of Measures
Mortality
Maturation
Regression to the Mean

Question 5

How is history a threat to IV?

Answer 5

Patient is exposed to a historic event and it affects the results.

Question 6

How is reliability of measures a threat to IV?

Answer 6

Unreliable measures can invalidate a study

Question 7

How is mortality a threat to IV?

Answer 7

Drop outs create unequal groups

Question 8

How is maturation a threat to IV?

Answer 8

Changes that occur in a study, study patients as time passes that is not caused by explanatory variables

Question 9

How is regression to the mean a threat to IV?

Answer 9

Extreme scores at the beginning of a study that migrate toward the mean as time passes

Question 10

What is another term for external validity?

Answer 10

Generalizability

Question 11

What is the extent to which results of a study are applicable to other populations, other settings and when implemented under different circumstances?

Answer 11

External Validity

Question 12

What is the measure of the effect of a specific treatment that may correlate with a real clinical endpoint but doesn’t necessary have a guaranteed relationship?

Answer 12

Surrogate Outcome Measures