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what is risk

chances of something happening - number of times something happened over the total number of times it could have


what is risk ratio

between two groups - control and clinical. the risk of clinical over the control


what is the absolute risk reduction

the difference in risks between two groups - control and clinical


if the risk ratio is 1, what does this suggest

that there is no difference between the risks of each group, therefore there is no difference in outcome between the control group and clinical group


what is the absolute risk difference

the difference between the risks of the two groups, the risk reduction. if this is 0 - no difference in outcome of the groups


what is a confidence interval

applying the risk ratio to the full population, instead of a sample population, the range of values of risk ratio is likely to lie when in a true population


when can confidence intervals suggest insufficient evidence for an outcome

if the confidence interval overlaps 1, the risk ratio could be 1 meaning the risks of outcome between the two groups could be equal, therefore there is no difference


when can a confidence interval suggest sufficient evidence for an outcome

if the CI does not overlap 1, either greater than or less than 1, there is a difference between the risks of outcomes between groups


if difference is looked at, what suggests insufficient evidence

a value overlapping 0 - no difference in values


describe a case study

when one patient or a group of patients are investigated, noting symptoms, treatment and outcome but not controlling anything, just reporting


describe a cross sectional study and what is it used for

when patients are looked at at a point in time, noting the number of patients with disease and on treatment, can be useful for prevalence of disease or identifying risk factors, only observational


describe a case-control study

having two separate groups - one with disease and one without. then investigating any differences, looking at risk factors. useful for looking at potential causes of disease, but can have recall bias


describe a cohort study

identifying a population - e.g. pregnant mothers - then following these participants, recording behaviour, measure exposure eg smoking, then looking at outcomes or diseases, e.g. premature birth, or congenital defects. very time consuming, might need a large sample size


describe a randomised control trial

having two separate groups and controlling all other variables. one clinical group and one control, randomly putting participants in each group and measuring outcomes. best way for causal effect, strong evidence on effectiveness of treatment


describe the four design elements of RCT

participant criteria - need to have an equal base line to start with, age, gender, disease
randomisation - participants should be randomly put into a group, done by a computer to avoid any bias.
control/comparison groups - placebo or current standard
blinding/masking - participant and investigator should not know what group they are in, knowing this might skewr results with bias


give some advantages and disadvantages of RCT

adv - strongest and best evidence for causality or effectiveness
disadv - if not random or blind, bias can over estimate results, difficult to design and conduct, cost and ethical issues


what type of study would be used to investigate the incidence of a disease

a cohort study - longitudinal design


what type of study would be used to investigate patients experience

cross sectional


what type of study would be used to investigate prevalence

cross sectional


what type of study would be used to investigate potential risk factors for disease

cohort or case control study


how do you decide whether to use a cohort or case control study

if rare disease, may be better to do case control - have the numbers of those with disease, with cohort, unsure if will get these numbers. If possible to get a large sample size, cohort but if not - case control. cohort could take years - costly