Biostatistics

Question 1

Specificity and Sensitivity of variant tests

Answer 1

highest sensivity at beginning of disease curve (point A)

highest specificity at end of healthy curve (point E)

Question 2

Alpha value

Answer 2

probability of type I error (rejecting a true null hypothesis)

Question 3

P-value

Answer 3

probability of obtaining a result as extreme as the given result while assuming the null hypothesis is true

indicates statistical significance

Question 4

Confidence intervals

Answer 4

chance that the difference between two groups reflects a true difference

Question 5

Case fatality rate

Answer 5

number of fatalities due to specific illness among all individuals with that illness

Question 6

Standard deviation

Answer 6

2 standard deviations = 95% if normal distribution

Question 7

Odds ratio

Answer 7

AxD/BxC

(A/B)/(C/D)

Question 8

ANOVA

Answer 8

compare means of 2 independent groups. will yield p-value but more difficult than t-test

Question 9

Chi-square test

Answer 9

analyze non-continuous data

Question 10

paired t-test

Answer 10

compare means of samples that are correlated (non-independent)

Question 11

2-sample t-test

Answer 11

analyze continuous data from 2 separate samples with normal distribution

Question 12

1-sample t-test

Answer 12

compare mean of single group to particular value (but not 2 groups)

Question 13

Recall bias

Answer 13

occurs in retrospective studies where participants are asked to recall past risk factors

Question 14

Performance bias

Answer 14

treatment that is administered differently at multiple sites

Question 15

lead-time bias

Answer 15

increased survival time due to earlier detection of disease (without a change in disease course)

Question 16

Skew on distributions

Answer 16

Positive skew : meAn > meDian > mOde

Question 17

What increases power of study?

Answer 17

increase sample size or increase effect size

Question 18

Cohort study

Answer 18

observational study , expansion of case series or cross sectional

provide estimate of incidence of a disease, outcome, or prognosis

strengthens by dissociating exposure from outcome

inefficient for diseases of long latency

Question 19

Accuracy

Answer 19

calculated by true positives and true negatives / total

Question 20

Case control study

Answer 20

usually retrospective

compares patients w/ dz to those w/o dz

look at past data to determine risk factors or exposure

Question 21

Cross-sectional study

Answer 21

observational study measures risk factor and outcome

compares different population groups at a moment in time

can compare multiple variables

does not determine causation

Question 22

Sampling bias

Answer 22

occurs in studies that recruit volunteers

Question 23

Expectancy bias

Answer 23

occurs when researcher knows which patients are distributed to which groups

researcher draws conclusions that support expected results

Question 24

Measurement bias

Answer 24

method of collecting data influences results

Question 25

Hawthorne effect

Answer 25

people act differently when they know they are being watched

Question 26

Relative Risk

Answer 26

probability of outcome of interest in exposed group / probability of outcome of interest in non exposed group