Biostatistics

Question 1

Types of Data: Can be _________ or ________

Answer 1

continuous or discrete/caterogorical

Question 2

Continuous data can be _________ or ________

Discrete/categoircal data can be _______ or _______

Answer 2

Continuous: ratio or interval

Discrete: nominal or ordinal

Question 3

what are measures of central tendency?

Answer 3

mean, median, mode

Question 4

mean is best for what kinds of data?

Answer 4

continuous or normally distributed values (no outliers!)

Question 5

median is best for what kind of data?

Answer 5

ordinal data or if there is SKEWED continuous data

Question 6

mode is best for what kind of data?

Answer 6

nominal data

Question 7

what is gaussian?

Answer 7

it is normal bell shaped distribution curve

Question 8

Gaussian distributions:
____% of values fall in 1 SD
____% of values fall in 2 SD

Answer 8

1 SD: 68%

2 SD: 95%

Question 9

alpha level:

used to select the maximum permissible ________

Answer 9

error margin

Question 10

alpha level:

commonly set at _____

Answer 10

5% of 0.05

if they do 1% of 0.01 — just need more data to prove this

Question 11

if the p-value is less than alpha: the null hypothesis is _______ and the result is termed statistically _______

Answer 11

null is rejected

statistically significant

Question 12

Confidence Interval = _____ - _____

Answer 12

1 - alpha

alpha of 0.05 = CI of 95%

Question 13

The CI range will not include _____ when comparing difference data/means

Answer 13

0

Question 14

The CI range will not include _____ when comparing ratio data (hazard ratio, odds ratio, hazard ratio)

Answer 14

1

Question 15

Type 1 errors: False _______

Type 2 errors: False ______

Answer 15

1: false POSTIVES – we rejected the null when we shouldn’t have
2: false NEGATIVES – we accepted the null when we should have rejected it

Question 16

Type 1 errors are related to (alpha or beta)

Type 2 errors are related to (alpha or beta)

Answer 16

1: alpha
2: beta (type 2 error = beta)

Question 17

Study power: 1 - ____

Power = the probability we will _____ the null hypothesis correctly

Answer 17

Beta (type 2 error)

we will REJECT correctly (aka power to avoid type 2 error)

Question 18

Risk – how to calculate?
vs
Relative risk — calculate it how?

Answer 18

Risk: # of subjects in group to have an event / total # of subjects in group….

RR: risk in exposed group (treatment)
divided by
risk in the control group

Question 19

Relative Risk Interpretation
RR = 1
RR > 1
RR < 1

Answer 19

1: no difference in outcome b/w groups
RR > 1 = greater risk for outcome in tx group
RR < 1 = lower risk/reduced risk of outcome in tx group

Question 20

Relative risk vs relative risk reduction?

Answer 20

RR: determines where the risk is less or more

RRR: indicates how much the risk was reduced

Question 21

How to find RRR? (relative risk reduction)

Answer 21

1 - RR

OR

% in control - % in tx group / % in control group

Question 22

ARR what is it and how to calculate it?

Answer 22

it is the reduction in risk and the incidence rate of the outcome

ARR = % risk in control group - % risk in tx group

Question 23

NNT what does it mean and how to find it?

Answer 23

NNT = number need to treat = how many patients need to be treated in a certain time frame for ONE patient to benefit

NNT = 1 / ARR
or NNT = 1 / (risk in control group - risk in tx group)

Question 24

For NNT calculations – if you get a fraction – round up or down?

Answer 24

always round up (this is conservative)

Question 25

For NNH calculations – if you get a fraction – round up or down?

Answer 25

always round down (this is conservative)

Question 26

NNH what does it mean and how to find it?

Answer 26

Number needed to harm = how many patients need to be treated in a certain time frame for ONE patient to be HARMED

NNH also is 1 /ARR (same as NNT)

Question 27

_______ test is good for nominal or ordinal data

Answer 27

chi square

Question 28

sensitivity the true _______
vs
specificity the true ______

Answer 28

sensitivity: true positive
specificity: true negative

Question 29

intention to treat vs per protocol?

Answer 29

intention: all pts originally put in the tx group are still included even when they did not complete it

per protocol: all include pts that completed the study