Statistics

Question 1

Likelihood Ratio

Answer 1

LR = Sensitivity /(1- Specificity)

Question 2

Post-test odd =

Answer 2

Pre-test odd x likelihood ratio (LR)

Question 3

Prevalence =

Answer 3

incidence x duration

Question 4

Power =

Answer 4

1 – the probability of a type II error

Question 5

The rapid COVID test has a sensitivity of 90% and specificity of 99%. If the prevalence of
COVID is 1 in 100, what is the approximate positive predictive value of the rapid COVID
test?

Answer 5

50%

Question 6

relative risk

Answer 6

EER / CER

Experimental event rate, EER
CER, Control event rate

Question 7

In a cohort study, the usual outcome measure is

Answer 7

Relative Risk

Question 8

Attrition Bias

Answer 8

a type of selection bias due to systematic differences between study groups in the number and the way participants are lost from a study

Question 9

Systematic Error vs Sampling Bias

Answer 9

Systematic bias is a consistent error that skews a sample in one direction, making it unrepresentative due to flaws in the sampling method, while sampling error is the random variation that occurs simply because a sample is used to estimate a population.

Question 10

variance vs coefficient of variation

Answer 10

Variance:
Average of squared deviations from mean
Measures absolute variability (spread of data)

Coefficient of variance:
Measures relative variability (spread compared to mean)
CV = SD/mean * 100

Question 11

Standard Error of the mean

Answer 11

a measure of how much the sample mean is likely to differ from the true population mean

= SD/ square root (number of population)

Question 12

Confidence interval calculation

Answer 12

Range likely containing true population value (CI = mean +/- 1.96 * SEM)

Question 13

How to reduce random error

Answer 13

Increasing sample size (random error is caused by chance)

Question 14

Prevalence vs incidence calculation

Answer 14

Prevalence = Existing cases/total population

Incidence = New cases/population at risk per time

Question 15

Odds to probability conversion

Answer 15

Odds = (probability / (1 - probability)

Question 16

Probability =

Answer 16

(Odds / ( 1+ odds)

Question 17

Prognostic vs predictive

Answer 17

Prognostic = disease recurrence, survival

Predictive = response to therapy

Question 18

Answer 18

Question 19

Relative risk reduction calculation

Answer 19

Question 20

Framing effect

Answer 20

Definition: Decisions or interpretations are influenced by how information is presented, even if the underlying facts are the same.

Question 21

Attribution bias

Answer 21

Definition: Explaining people’s behavior based on personal traits rather than situational factors.