equal chance of being allocated to EG and CG - good when highlighting differences in a drug trial - reduce chances of confounding

NOTES FOR POPHLTH MOD 1 Flashcards by Joan Waipouri

Epidemiology

Frequency of health and disease in different populations- causes of poor health and how to improve

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Epidemiology equation

E= (N/D) / T

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GATE standards for what?

Graphic approach to epidemiology

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Cohort study “observational follow up”

CG and EG have measurements/observations

Outcomes over a period of time- can measure incidence and prevalence

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Incidence (OUTcome measurement)

Events that occur are counted forward from starting point OVER PERIOD OF TIME

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Prevalence (OUTcome measurement)

Disease are counted at ONE POINT IN TIME. time is not included

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Describe incidence overview

easy to measure
categorical measure eg” death’ gender”
NOT NUMERICAL value
depends only on the number of events

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Prevalence overview

hard to measure
numerical and categorical measures
depends on how much event occur and how death and cure occur

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Describe cross sectional studies

Exposure and outcome are measured at the same point in time- eg checking pulse rate

Good to measure the prevalence within a group

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Describe the overview of Cohort study

have measurements
over period of time
can measure incidence and prevalence

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Strengths of Incidence

Clean measure as its only determined by risk-

includes N/D/T

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Weaknesses of Incidence

Difficult to measure as its over time

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Weakness of prevalence

Less informative only includes N/D

determined by incidence cure rate and death rate

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Strengths of Prevalence

easy to measure as you stop time and count

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Describe RCTS

Are like cohort studies but allocated randomly to EG and CG

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Strength of RCTS

equal chance of being allocated to EG and CG

good when highlighting differences in a drug trial
reduce chances of confounding

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What is a double blind RCT

Participants/ investigators are both unaware

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What are the requirements of RCTS

they can only be completes if they are ethical and practical-

Large studies are expensive

Drugs must not harm

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what is RD

EGO- CGO

also known as the absolute risk difference

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RR= 0 meaning?

EGO= CGO and there is no difference

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RISK ratio

EGO/ CGO

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Describe RR and how to compare it

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RR has no units
if RR is less than 1 it = RRR
if RR is more than 1 = RRI
this is seen as a percentage

Acronym for non random error

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R A M BOM AN- used in non random error

Describe R

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REcruitment
who they are
do they represent the population
what is the response rate like

Describe A

ALLocation how well were participants allocated how were they allocated was it subjective- questionaire or objective- measurement

Describe ADjustment in Analyses

separating the factors that influence bias

Describe confounding

exposure is mixed with another factor which will affect the outcome

Describe M

maintenance did participants remain in there groups= EG and CG were any groups lost in follow up

Describe Cross sectional studies relationship with M

Maintenance is not an issue- follow up does not affect outcome

Describe blind or Objective measurement

Objective is measure- not affected by personnel interpretation questionnaire is subjective- people have different opinions Double blind studies are good to reduce error

What is Confounding's relationship with studies

will always influence all ecological studies

Describe RAndom error causes

everyone can not be studied identical studies will have different results Occurs when there is a smaller sample= greater chance results will not represent the population

Describe the 95% confidence interval

95% chance the true value in a population lies within the 95% confidence interval -range of results likely to include the true results in the whole population

Describe the 95% CI interval on a chart

If EGO and CGO do not overlap and 95% of CI does not overlapRD= 0 or RR= 1= Statistically significant If EGO and CGO overlap and CI of RR=1 overlap RD= 0 this means there is NO significant difference

What decreases the chances of Random error

A bigger study= less random error

WHat is a method that can be used instead of a bigger study to decrease Random error

Meta analysis

describe Meta analysis

take multiple studies and put them together

ECOlogical studes and Error

most common error Maintenance prone to confounding difficult to adjust

Cross sectional studies and error Strength

Strength: recruitment Measurement- if self reported little to none maintenance error quick and cheap Weaknesses: Reverse causality/ confounding

Cohort study and error/ strengths/ weaknesses

easier to adjust and manage cohort in analyses Strength: provides relationship between exposure and outcome W: prone to confounding Maintenance error

RCTS and error

Minimal confounding- meta analysis maintenance error common if long-term Very expensive= difficult to do so

RD or absolute risk is known as what?

EGO- CGO

What is the no equivalent effect value

RD= 0 or RR= 1

What are the 4 types of random error that can occurr

R sampling error R measurement error Inherent biological gradient R allocation error

Describe R sampling error and how to reduce it

a study population can never be identical. Results will produce an estimate of the truth in the population To reduce it: averaging

Describe R measurement error and how to reduce it

it is difficult to measure biological gradients the same each time It is hard for a human to measure each time Reduction via averaging

Describe R allocation error and how to reduce it

Only exists with RCTS. Groups may differ by baseline by chance Reduction: Bigger sample

Describe Inherient Biological randomness and how to reduce it

Biological phenomena are inherently random. Therefore a individuals measurement can change from time to time How to reduce it: averaging

What is reverse causality

occurs when a relationship between EG and CG cannot be established.

What occurs when the risk difference is lower in the exposure group

results in an absolute risk reduction

What occurs when the risk difference is higher within the exposure group

results in a absolute risk increase

Describe stratified analysis

confounding can be reduced if participants are placed in different age groups. if age groups= no difference= confounding has not occurred. If age group= difference in numbers= confounding has occured

Describe AN within Ramboman

are differences between EG and CG adjusted for within the analysis

NOTES FOR POPHLTH MOD 1 Flashcards

(53 cards)