Terminology

Question 1

Define representative sample

Answer 1

sample of the pop whose characteristics are representative of those in the larger pop

Question 2

Define random sample

Answer 2

sample not representative of the pop

Question 3

Define incidence

Answer 3

new cases

is a rate

units of person-years or per person per year

Question 4

Define prevalence

Answer 4

total number of cases

is a proportion

has no units

Question 5

Define ratio vs proportion

Answer 5

ratio = one number divided by another

proportion = fraction where the top part has to be part of the bottom

Question 6

Define rate vs ratio

Answer 6

rate = number of events per population per time

ratio = comparison (rates or odds)

Question 7

Define ratio of benefit vs ratio of harm

Answer 7

benefit = 1/ratio of harm

harm = 1/ratio of benefit

Question 8

Define confounding

Answer 8

becomes an issue when 2 groups are being compared

influences the measure of association = misinterpretation

associated with both factors

Question 9

Define bias

Answer 9

samples being studied are diff or are being treated diff

e.g. selection bias, info/measurement bias

Question 10

Define 95% confidence interval

Answer 10

range in which we can be 95% certain that the true value of underlying tendency really lies

Question 11

Define p-value

Answer 11

probability of getting an observation as extreme as, or more extreme than one observed assuming that the stated hypothesis is true

Question 12

Define prospective study

Answer 12

watches for outcomes

cohort

Question 13

Define retrospective study

Answer 13

looks backwards and examines exposures in relation to an outcome that is established at the start of the study

cohort
case-control

Question 14

Define random selection

Answer 14

recruitment into a clinical trial and affects external validity

Question 15

Define random allocation

Answer 15

allocation between treatment groups in a clinical trial and affects internal validity

Question 16

Define as-treated

Answer 16

analysis according to what the trial participants did

this assesses the physiological effects of treatments studied

Question 17

Define intention-to-treat

Answer 17

analysis according to the original allocation of the participants

this preserves the original random allocation, reduces bias and reflects what would happen in practise

Question 18

Define forest plot

Answer 18

graphical representation of a meta-analysis

each study shown by varying sized square

horizontal lines runs through square to represent confidence interval

diamond symbol used to represent the overall estimate from the meta-analysis

Question 19

Define funnel plot

Answer 19

used to check existence of publication bias in a systematic review

its assumes the spread of studies is symmetrical

variation from the assumption can indicate publication bias

Question 20

Define homogeneity

Answer 20

null hypothesis = there is no variability between the studies in the systematic review

Question 21

Define heterogeneity

Answer 21

statistical heterogeneity = variation as a result of the observed intervention effects, being more diff than we would expect due to chance alone

Question 22

Define systematic review

Answer 22

used to appraise, summarise and communicate large quantities of research on a similar topic

qualitative or quantitative

Question 23

Define meta-analysis

Answer 23

stat tool used to combine evidence and quantify the results

Question 24

Define fixed effect

Answer 24

we assume that all the included studies share a common side effect

observed effects will be distributed about the common effect size, with a variance that depends primarily on the sample size for each study

Question 25

Define random effect

Answer 25

rather than assuming that the studies share a common effect, we assign a distribution of effect sizes

Question 26

Define publication bias

Answer 26

bias towards publishing studies according to whether they show statistically significant results

Question 27

Define statistical significance

Answer 27

whether the p-value is less than or greater than 0.05

if we are looking at the diff between a new intervention and a comparison then a p-value less than 0.05 will result in a conclusion that the intervention is more effective than the comparison group

Question 28

Define clinical significance

Answer 28

determined by the minimally clinically important difference between the 2 groups.