HaD Pop.txt
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What types of bias are there?
 Information bias
 Recall bias
 Selection bias

What is information bias?
 Differences in measurement in the groups
 Correct people wrong info

What is recall bias?
Differences in the groups due to forgetting info

What is selection bias?
Wrong people correct info

What is confounding?
A factor associated with the exposure and disease of interest but not itself on the causal pathway

What is Incidence rate?
Number of new cases of a disease in a defined population in a defined period of time

What is prevalence?
Proportion of people affected in a defined population at a particular point in time

What is a cohort study?
 Identify based on exposure then monitor disease outcome
 Suitable for rare exposures
 Less prone to bias
 Expensive
 Problems with follow up
 Analyse with incidence rate ratio and smr for external comparison
 Can be prospective or retrospective

What is a case control study?
 Identify on disease outcome and compare exposure
 Suitable for rare diseases
 Cheaper
 Problems with recall and selection bias
 Analyse using odds ratio then estimate relative risk

What is a randomised control trial?
 Comparison of two treatments interventions or a placebo chance determins who gets what and it is planned
 Can be ethical problems

What is a systematic review?
 Overview of primary studies that used explict and reproducible methods
 Uses bradford hill criteria

What is a metaanalysis?
Mathematical synthesis of two or more primary studies that addressed the same hypothesis in the same way

What are the advantages of a systematic review?
 Limit bias
 Increase prescision of overall result
 Large amounts of info can be understood quickly
 Results of studies can be compared
 Reasons for inconsistencies can be identified

Limitations of systematic reviews?
 Dependant on quality of primary studies
 Susceptible to publication bias
 Reader still needs to consider generalisability of the result

What is the observed incidence rate ratio?
=observed incidence rate in pop 1/ observed incidence rate in pop 2

What is the odds ratio?
 Measure of the risk of disease in one group compared to another
 =exposed disease x unexposed no disease/unexposed disease x exposed no disease

What is the standard mortality ratio?
 = (observed/expected)x100
 Smr >100 means more incidence than expected

What is the error factor?
 Measure of random variation
 Large error factor can be due to small sample size
 = exp(2xsquare root[(1/d1) + (1/d2)])

What is the 95%confidence interval?
= from the obseved value / error factor to the observed value x by the error factor

What is the pvalue?
 A measure if how likely the results are due to chance
 If 95% CI excludes the null hypothesis value of 1...
 P<0.05
 reject null hypothesis
 There is evidence of a difference
 Result is not due to chance

What is evidence base medicine?
 Use of best current evidence in making descisions about the care of individual patients
 Involves the integration of best clinical expertise best evidence from research and patients unique values and circumstances

What are the levels of evidence?
 Systematic review of RCTs
 RCT
 Well designed trial
 Well designed non experimental study
 Respected authority