Module 1; Measuring health and dis-ease in populations

Question 1

what is the equation for the frequency of disease?

Answer 1

N/D/T

Question 2

what is the gate frame made up of?

Answer 2

PECOT (population, exposure, comparison, outcome, time)

Question 3

does the gate frame require all components of PECOT?

Answer 3

no, not all the time

Question 4

what is a cohort study?

Answer 4

group of participants that are allocated into several groups (EG/CG) and followed up over a period of time

Question 5

are cohort studies observational or experimental?

Answer 5

observational, and not random

Question 6

do cohort studies measure incidence or prevalence

Answer 6

both

Question 7

what is a cross sectional study

Answer 7

outcome + comparison at the same time, calculates the average

Question 8

do cross sectional studies measure incidence or prevalence?

Answer 8

prevalence

Question 9

do incidence studies count categorical or numerical events?

Answer 9

categorical

Question 10

do prevalence studies count categorical or numerical events?

Answer 10

both

Question 11

what are some problems with the incidence/prevalence

Answer 11

1. change if high incidence, low prevalence (people dying)
2. change if low incidence, high prevalence (obesity)

Question 12

advantages/disadvantages of prevalence

Answer 12

easy + cheap to measure

only numerator + denominator
dirty because of cure rate and health rate

Question 13

advantages/disadvantages of incidence

Answer 13

difficult and expensive to measure

only determined by a disease risk in a population
number, denominator and time measured

Question 14

what are RCTS?

Answer 14

random controlled trials
cohort studies, but participants are randomly allocated

Question 15

are cohort studies ethical?

Answer 15

yes because they are observing, not experimenting
however these are less accurate than experimental

Question 16

risk difference

Answer 16

ego-cgo

Question 17

risk ratio

Answer 17

ECO/CGO

Question 18

differences between risk difference and risk ratio

Answer 18

risk difference
- has units

risk ratio
- has no units
- rr reduction, RR > 1
- rr deduction, RR < 1

overall risk difference > risk ratio because its more accurate.

Question 19

errors in epidemiological studies

Answer 19

random error (chance)
non random error (systematic error)

Question 20

what is the acronym for non random errors?

Answer 20

RAMBOMAN

Question 21

Ramboman

Answer 21

recruitment
- representative of the whole population? selection bias

Question 22

rAmboman

Answer 22

allocation
- usually by measurement or by random allocation
measurement ; e.g. measurement smokers vs drinkers. questionnaire

random allocation; prevents bias
- reduces effect of counding
- random trials = lots of effort and learning

Question 23

raMboman

Answer 23

maintenance
long experiment > short experiment.
participants may not stay in allocated groups
participants lost to follow up
not a problem in prevalence bc its a one time measure

Question 24

ramBoman

Answer 24

double blind vs single blind
double blind prevents doctors from having a trait to distract their feeling

Question 25

rambOman

Answer 25

objective - should have no confusion in interpretation + subjective words can be confusing - ecological studies can struggle w this bc different words are subjective

Question 26

what are ecological studies

Answer 26

allocation of whole population rather than individuals e.g. average __ levels

Question 27

what is a problem with ecological studies + how to combat

Answer 27

confounding!!! to combat ; use ecological randomised trials.

Question 28

something special about cohort studies

Answer 28

they can start as cross sectional, and then follow up to become cohort

Question 29

can cross-sectional studies change?

Answer 29

no they stay cross-sectional

Question 30

what are the strengths and weakness of ecological studies?

Answer 30

+low random error +cheap - confounding common

Question 31

what are the strengths and weaknesses of rcts?

Answer 31

-difficult to to have representative sample, population are often highly motivated volunteers +random allocation!! -confounding -unethical to subject ppl to harm -maintenance error common -expensive + small

Question 32

strengths and weaknesses of cross sectional

Answer 32

+easier to recruit -confounding common +ethical +maintenance error not an issue +less expensive -only measure prevalance --reverse causality (which came first?? exposure/outcome)

Question 32

strengths and weaknesses of cohort studies

Answer 32

+easier to recruit rep pop - more confounding errors +ethical to study harm -maintenance error common +less expensive than rct +can measure incidence + prevalence

Question 32

how to choose bt study designs

Answer 32

depends on question + what is possible (ethicality, practicality, affordability)

Question 33

what is a meta-analysis

Answer 33

mathematical combination of studies bc they are too small by themselves

Question 34

strengths + weaknesses of meta analyses

Answer 34

low random error + depends on quality of steps

Question 35

what are the two types of random error?

Answer 35

random measurement error (human error) random sampling error (not representative of the whole population

Question 36

95% confidence interval

Answer 36

there is about a 95% chance that a true value in a population lies within the 95% confidence interval in 100 identical studies using samples from the same population, 95/100 of the 95% cis will include the true value

Question 37

what is statistically significant?

Answer 37

if ego/cgo dont overlap OR the 95% rr/rd does not overlap the no error line (which is when cgo=ego)

Question 38

statistically insignificant

Answer 38

when ego/cgo overlap or rr/rd overlaps with the no error line