BIOSTATS

Question 1

sensitivity

Answer 1

True Postives / TP + FN, aka the true positive rate.
out of all those who have the disease, how many test positive
Rules in a disease

Question 2

specificity

Answer 2

True Negatives / TN + FP
Out of those without the disease, how many test negative

Question 3

Postivie Predictive Value

Answer 3

Out of all the positives, which are true?
TP/ TP + FP

Question 4

Negative Predictive value

Answer 4

out of all of those that test negative, which are true?
TN/ TN + FN

Question 5

Incidence

Answer 5

How many new diagnoses for a condition in a year or specified time

Question 6

prevalence

Answer 6

how many people who have the disease at any given time

Question 7

Case control

Answer 7

Study that has a group with a disease and a comparative group without and they look back into history to evaluate exposures. This provides an odds ratio. Good for rare diseases.

Question 8

Odds Ratio

Answer 8

From Case Control Studies
Odds Ratio:
odds of having the disease given an exposure/ Odds of not having the disease given an exposure

If youre using the table with disease on the top, exposure on the side, ++ top left corner and A–>B on top boxes and C–> bottom boxes, then the equation is:

(a/c) / (b/d) also the same as ad/bc

THESE ARE ODDS not PROBABILITY

Question 9

What number can you get from a cohort study?

Answer 9

Relative Risk

Question 10

Relative Risk

Answer 10

from cohort study:
similar to odds ratio probability of having the disease and having the exposure/ probability of having the disease and not having the exposure
a/ a+b / c/c+d

Question 11

Case control is based on ____________ outcomes, its good for rare diseases

Answer 11

known outcomes

Question 12

power

Answer 12

1-Beta

Question 13

increasing sample size or precision of measuring outcomes will result in

Answer 13

decreasing type II errors

Question 14

Attributable risk

Answer 14

The absolute risk attributable to exposure in the exposed group. Calculated as: incidence rate in the exposed group - incidence rate in unexposed group

a/(a + b) - c/(c + d)

used in cohort studies

Question 15

The difference in risk attributable to an exposure as compared to non-exposure

Answer 15

risk in non-exposed group – risk in exposed group

c/(c + d) – a/(a + b)

essentially attributable risk flipped

Question 16

An epidemiological measure of risk that refers to the proportion of decreased risk due to an intervention compared to the control group.

Answer 16

Relative risk reduction

Question 17

Relative risk reduction

Answer 17

An epidemiological measure of risk that refers to the proportion of decreased risk due to an intervention compared to the control group.

1 - RR

Relative risk (RR): (a/(a + b))/(c/(c + d))

Question 18

Number needed to treat (NNT)

Answer 18

1/ARR

Question 19

Number needed to harm (NNH)

Answer 19

1/AR

Question 20

RR = 1

Answer 20

Exposure neither increases nor decreases the risk of the defined outcome

Question 21

RR > 1

Answer 21

Exposure increases the risk of the outcome

Question 22

RR < 1

Answer 22

Exposure decreases the risk of the outcome.

Question 23

OR = 1

Answer 23

The outcome is equally likely in exposed and unexposed individuals

Question 24

OR >

Answer 24

The outcome is more likely to occur in exposed individuals

Question 25

OR < 1

Answer 25

The outcome is less likely to occur in exposed individuals

Question 26

Case-control studies do not track participants over time, so they cannot be used to calculate relative risk. However, the assumption can be made that if an outcome (e.g., disease prevalence) is rare, the incidence of that outcome is low and the _______ is approximately the same as the ______.

Answer 26

Case-control studies do not track participants over time, so they cannot be used to calculate relative risk. However, the assumption can be made that if an outcome (e.g., disease prevalence) is rare, the incidence of that outcome is low and the OR is approximately the same as the RR.

Question 27

what is the difference between RR and HR?

Answer 27

The RR is the risk of an event occurring by the end of the study period (i.e., cumulative risk), while the HR is the risk of an event occurring at any point in time during the study period (i.e., instantaneous risk).