Step 3 Biostats

Question 1

TP / (TP + FP)

higher when disease prevalence is high

Answer 1

PPV = TP / (TP + FP)

the probability that a person with a positive test result has the disease

Question 2

TN / (TN + FN)

higher when disease prevalence is low

Answer 2

NPV = TN / (TN + FN)

the probability that a person with a negative test result is disease-free

Question 3

TP / (TP + FN)

Answer 3

Sensitivity = TP / (TP + FN)

probability that a person with a disease will have a positive test result

Question 4

TN / (TN + FP)

Answer 4

Specificity = TN / (TN + FP)

probability that a person without a disease will have a negative test result

Question 5

(risk, exposed group) / (risk, unexposed group)

Answer 5

RR = (risk, exposed group) / (risk, unexposed group)

Question 6

(CER - EER) / CER

Answer 6

RRR = (CER - EER) / CER

Question 7

CER - EER

Answer 7

ARR = CER - EER

Question 8

1 / ARR

Answer 8

NNT = 1 / ARR

Question 9

Standard Deviation of a Normal Distribution

?% are within one SD
?% are within two SD
?% are within three SD

Answer 9

Standard Deviation of a Normal Distribution

68% are within one SD
95% are within two SD
99.7% are within three SD

Question 10

Failure to reject a null hypothesis when it’s false; depends on sample size

Answer 10

Type II Error

Question 11

Overestimation of survival among sreening-detected cases caused by relative excess of slowly progressing cases (individuals with rapid disease progression don’t live to be screened)

Answer 11

Length Time Bias