Session 1 Flashcards
What is the definition of prevalence?
Proportion of people who have a disease at a given point in time
What is incidence?
Number of new cases of a disease within a given timeframe, often reported as a rate
What are 2 types of error that can occur in a study that may influence the results?
Chance (random error)
Bias (systematic error)
What is chance or random error?
Due to sampling variation, will reduce as sample size increases (reduce uncertainty, increase precision)
What is bias or systematic error?
Bias is quantified by difference between the true value and the expected value, does not reduce as sample size increases
What are 2 sources of bias?
Selection and information bias
What are 3 types of selection biases?
Study sample - not representative of whole population
Group selection within study - not comparable
Healthy worker effect - workers have lower overall mortality
What are 4 types of information biases in data?
Recall error - participants recall differently
Observer error - preconceived expectations that may influence
Measurement error - different measurement of participants
Misclasssification - participants put in the wrong group
What is risk difference?
Absolute difference in risk between one group and another
What is relative risk or risk ratio?
Comparison of probability of an event occurring in one group compared to another
What is odds ratio?
Odds ratio is a relative comparison of the odds of disease in group A compared to group B
What is the difference between absolute and relative risk?
Absolute risk is a proportion, relative risk is a ratio of proportions
What is confounding?
When comparing groups, the association or effect between an exposure and outcome is distorted by the presence of another variable
