Biostatistics

Question 1

What is outcome measurement of a case-control study

Answer 1

Odds ratio

Question 2

What is outcome measurement of a cohort study

Answer 2

Relative risk

Question 3

Phase III vs Phase IV study

Answer 3

Phase IV is postmarketing surveillance (after approval); detects rare or long-term adverse effects

Question 4

Sensitivity formula

Answer 4

True positive rate: TP/TP+FN

Question 5

Specificity formula

Answer 5

True negative rate: TN/TN+FP

Question 6

What parameter must be high for a screening test

Answer 6

Sensitivity

Question 7

What parameter must be high to rule in a disease

Answer 7

Specificity

Question 8

Positive predictive value formula

Answer 8

TP/TP+FP

Question 9

What happens to PPV as prevalence increases

Answer 9

higher PPV

Question 10

Negative predictive value formula

Answer 10

TN/FN+TN

Question 11

What happens to NPV as prevalence increases

Answer 11

lower NPV

Question 12

Incidence vs prevalence

Answer 12

Incidence= new cases
Prevalence= all current cases
(prevalence higher for chronic diseases)

Question 13

Formula for Odds ratio

Answer 13

Odds that disease expose/odds without disease exposed

OR=ad/bc

Question 14

Formula for relative risk

Answer 14

Risk developing disease in exposed/risk developing disease in unexposed
RR=a(a+b)/c/(c+d)

Question 15

When are OR and RR similar

Answer 15

when prevalence is low

Question 16

Formula relative risk reduction

Answer 16

1-RR

Question 17

Attributable risk formula

Answer 17

difference in risk between exposed and unexposed

AR=a/a+b-c/c+d

Question 18

Absolute risk reduction

Answer 18

difference in risk attributable to intervention as compared to control

Question 19

Number needed to treat formula

Answer 19

1/ARR

Question 20

Number needed to harm formula

Answer 20

1/AR

Question 21

Random error reduces___

Answer 21

precision

Question 22

systematic error reduces___

Answer 22

accuracy

Question 23

Multiple/repeated studies, crossover studies, matching help reduce___ bias

Answer 23

confounding bias

Question 24

Berkson bias

Answer 24

selection bias of hospitalized patients (have incr risk of exposure-throws off OR)

Question 25

Hawthorne effect

Answer 25

groupes that know they are being studied behave differently; measurement bias

Question 26

how prevent lead-time bias

Answer 26

measure “back-end” survival

Question 27

Standard deviation vs SEM

Answer 27

SEM=mean/Square root(n)

Question 28

Gaussian distribution

Answer 28

bell-shaped, mean=median=mode

Question 29

Incr sample size, effect size, precision of meausrement

Answer 29

all incr power

Question 30

Define Type 1 error

Answer 30

or a: stating there is an effect when none exists

Question 31

Define Type II error

Answer 31

or b: stating there is not an effect when one exists

Question 32

For 95% CI, Z=?

Answer 32

1.96

Question 33

For 99% CI, Z=?

Answer 33

2.58

Question 34

% within one SD

Answer 34

68%

Question 35

% within two SD

Answer 35

95%

Question 36

% within three SD

Answer 36

99.7%

Question 37

What checks the difference between the mean of 2 groups

Answer 37

T-test

Question 38

What checks the difference between the mean of 3+ groups

Answer 38

ANOVA

Question 39

What checks the difference between 2+ categorical outcomes

Answer 39

Chi squared