Lecture 4, part 6

Question 1

Definition of internal validity

Answer 1

An instrument’s ability to measure what it intends on measuring

Question 2

Definition of sensitivity

Answer 2

Ability of a test to correctly diagnose persons who have preclinical dz as test-pos
-The probability of testing positive if the dz is truly present

Question 3

Formula for sensitivity

Answer 3

True positives/true positives + false negatives

Question 4

Definition of specificity

Answer 4

Ability of a test to correctly categorize persons without preclinical dz as test-neg
-The probability of testing negative if the dz is truly absent

Question 5

Formula for specificity

Answer 5

True negatives/true negatives + false positives

Question 6

Definition of positive predictive value

Answer 6

Proportion of ppl who truly have the dz out of all those who screen positive for the dz

Question 7

Formula for positive predictive value

Answer 7

True positives/true positives + false positives

Question 8

A valid test is always ________

Answer 8

Reliable

Question 9

When does positive predictive value increase?

Answer 9

With increasing prevalence, not part of testing validity

Question 10

When screening for dz with low prevalence, most pos test results will be _________

Answer 10

False-positives

Question 11

Are sensitivity and specificity dependent on prevalence?

Answer 11

No

Question 12

On what does the prevalence of dz depend?

Answer 12

Incidence rate of the condition
Avg length of the pre-clinical phase
Whether screened previously

Question 13

What should be done to increase positive predictive value?

Answer 13

Screen high risk pops