Statistics

Question 1

First trials in humans, single sub-therapeutic doses given

Answer 1

Phase O drug design
- primarily to gain pharmacokinetics and pharmacodynamics data

Question 2

Healthy volunteers trial medication to determine safe dosing ranges and identify some adverse effects

Answer 2

Phase I drug design

Question 3

100-300 participants, confirming dosing requirements and efficacy

Answer 3

Phase II drug design
Dosing requirements = IIa
Efficacy = IIb

Question 4

100-1000s of participants, confirm safety and efficacy of drug

Answer 4

Phase III drug design
Confirm effectiveness vs placebo/active treatments (“gold standard”)
Involve regulators (e.g. FDA) to obtain approval

Question 5

Continued pharmaco-vigilance, trial of new uses/populations, involvement of paediatric patients

Answer 5

Phase IV drug design
Larger populations but less controlled, longer follow up
Assess interactions with other medications

Question 6

Greatest strength of case control studies?

Answer 6

Multiple risk factors can be assessed

Question 7

Greatest threat to validity in longitudinal cohort study?

Answer 7

Loss to follow up

Question 8

Study looking at exposures in patients with known disease?

Answer 8

Case control

Question 9

Evaluation of participants with known exposure of interest?

Answer 9

Cohort study

Question 10

Major strength of RCTs?

Answer 10

Minimises bias and confounding

Question 11

Which research design can most conclusively demonstrate causality?

Answer 11

RCT

Question 12

Test which evaluates if there is a significant difference between expected frequencies and observed frequencies in one or more sets of categorical data

Answer 12

Chi-square test

Question 13

The degree of which two variables are related

Answer 13

= correlation

Question 14

Test which compares the means of two different samples of data which have a normal distribution

Answer 14

Student’s t-test

Question 15

Test determines whether there is statistically significant differences between the means of three or more independent variables

Answer 15

= analysis of variance

Question 16

Type I error

Answer 16

False positive

Question 17

Type II error

Answer 17

False negative
i.e. failure to reject an incorrect null hypothesis

Question 18

Feature of a meta-analysis indicating minimal or no bias in the results?

Answer 18

Statistical heterogeneity

Question 19

In what circumstances does an odds ratio approximately equal a relative risk ratio for a disease in the population?

Answer 19

Low prevalence of disease
- OR is a ratio of odds, whereas relative risk is a ratio of the two probabilities
- OR would exaggerate the risk if the disease is more common than 10%

Question 20

What is risk reduction?

Answer 20

Difference in event rates between the control and experimental groups expressed as a proportion of the event in the untreated group

Question 21

How to adjust for multiple comparisons in a study?

Answer 21

Bonferroni correction

Question 22

Best way to reduce random error in a study?

Answer 22

Increase sample size

Question 23

Definition of the p value

Answer 23

Probability of obtaining the test result observed under the assumption that the null hypothesis is true
i.e. the probability that an observed difference could have occurred by chance

Question 24

Standard error

Answer 24

A measure of the accuracy of the sample estimate (i.e. the larger the sample size, the more likely this accurately reflects the population, so the smaller the sample error)

Question 25

Terms used to describe standard deviations from the mean

Answer 25

Sigma score
Standard score
Z score

Question 26

Measurements used for variability of data?

Answer 26

Range, interquartile range, standard deviation

Question 27

Logistic vs linear regression

Answer 27

Both used to find a relationship when there are multiple variables
Logistic regression = binary outcomes (e.g. presence of disease)
Linear regression = continuous outcomes (e.g. oxygen requirement)

Question 28

Which measure of association is typically used for survival analysis?

Answer 28

Hazard ratio

Question 29

Best measure to describe the frequency of occurrence of disease in the investigation of an epidemic?

Answer 29

Prevalence

Question 30

Positive predictive value

Answer 30

Calculation of true positive rate in total positive test outcomes
(True positive/All positive results)

Question 31

Negative predictive value

Answer 31

Calculation of true negative test results within total negative test outcomes
(True negative/All negative results)

Question 32

Sensitivity

Answer 32

Ability of a test to detect disease
= True positive test results / Positive for condition
If highly sensitive test is negative = rule out

Question 33

Specificity

Answer 33

Test which correctly identifies people without disease
= True negative test result / Patients without disease

Question 34

Positive likelihood ratio

Answer 34

= Sensitivity / (100% - specificity)

Question 35

Negative likelihood ratio

Answer 35

= (100% - sensitivity) / specificity

Question 36

Absolute risk reduction calculation

Answer 36

(events in controls/total controls) - (events in treatment/total treatment)

Question 37

Number needed to treat

Answer 37

NNT = 100 / ARR (%)

Question 38

Number needed to harm

Answer 38

NNG = 100 / absolute risk increase (%)

Question 39

Odds ratio

Answer 39

(ad) / (cb)