Stats

Question 1

Define case control study

Answer 1

Match groups of affected people with unaffected people and retrospectively assess risk factors/exposures

Question 2

Define retrospective and prospective cohort study

Answer 2

Retrospective - taking group of affected people and looking at previous RFs/exposures
Prospective - take group of unaffected people and follow over time for risk factors/exposures and development of disease

Question 3

Define sample bias

Answer 3

Group of selected patients don’t accurately represent the population (ie tertiary hospital setting)

Question 4

Define participation bias

Answer 4

Volunteers for clinical trials often don’t represent general population

Question 5

Define measurability bias

Answer 5

Trial investigators not being blinded to intervention and therefore may skew results to become meaningful

Question 6

Recall/reporting bias

Answer 6

Problem with retrospective trials, exposure history may not be accurately recalled or reported

Question 7

Exclusion bias

Answer 7

Drop outs not being included in results

Question 8

What percentage of data points are one standard deviation away from the mean? Two? Three?

Answer 8

1 SD = 67%
2 SD = 95%
3 SD 99.7%

Question 9

Equation for standard error of the mean

Answer 9

Standard deviation / sqroot(sample size)

Question 10

What is p-value definition?

Answer 10

Probability that result occurred by chance

Question 11

What is type 1 error?

Answer 11

Incorrectly rejecting the null hypothesis (false positive)

Question 12

What is type 2 error?

Answer 12

Missing a true correlation due to an underpowered study (false negative)

Question 13

Calculation for RR

Answer 13

RR = Risk (exposed) / Risk (control)

Question 14

Calculation for ARR

Answer 14

ARR = Risk (control) - Risk (exposed)

Question 15

Calculation for NNT

Answer 15

1 / ARR

Question 16

Odds equation for intervention group

Answer 16

Odds (intervention) = n (affected in intervention group) / n (unaffected in control group)

Question 17

Odds equation in control group

Answer 17

Odds (control) = n (affected in control group) / n (unaffected in intervention group)

Question 18

Odds ratio equation

Answer 18

Odds (intervention) / odds (control)

Question 19

Define sensitivity

Answer 19

Proportion of people that have disease that correctly test positive

Question 20

Define specificity

Answer 20

Proportion of people that don’t have the disease that correctly test negative

Question 21

Positive likelihood ratio equation

Answer 21

Sensitivity / (1 - specificity)

Question 22

Negative likelihood ratio equation

Answer 22

(1 - sensitivity) / specificity

Question 23

Does likelihood ratio use odds or probability?

Answer 23

Odds

Question 24

Equation for pre-test odds

Answer 24

Pre-test prob / (1 - pre-test prob)

Question 25

Equation for post-test probability

Answer 25

Post-test odds / (1 + post-test odds)

Question 26

Calculation for post test odds

Answer 26

Pre-test odds x LR

Question 27

Pre-test probability is the same as

Answer 27

Prevalence