Statistical Description of Risk Flashcards
What does risk mean?
The probability of something occurring in a sample (group) or population.
What are the 2 main types of risk?
Absolute
Relative
What does absolute risk mean?
This is the probability of an event occurring = events / number of people in sample or population.
What does relative risk mean?
This is the probability of an event occurring in one group compared to another = absolute risk 1 / absolute risk 2.
What does odds mean?
This is the chance of an event occurring compared to it not occurring in one sample or population.
What does odds ratio mean?
Comparison of odds of an event occurring between groups.
What 2 main categories do we use risks and odds for?
Observational Studies
Randomised Controlled Trials
What is considered under observational studies?
Cohort Studies
EG: Exposure = Smoker or non smoker
Outcome = Lung Cancer or not
What is considered under randomised controlled trials?
Exposure = Trial Drug or Placebo Outcome = Event or No event
How do you calculate the absolute risk?
Number of events (good // bad) divided by the number of people in that group.
How are absolute risks expressed?
They are expressed as percentages.
How do you calculate odds?
Number of events divided by the number of non - events.
How are odds expressed?
They are expressed as decimals or simple fractions.
How do you calculate the relative risk?
Absolute risk for Group 1 / Absolute risk for Group 2.
How do you calculate the odds ratio?
They are expressed as Odds for Group 1 / Odds for Group 2.
What are confidence intervals?
A range of values for a parameter that is likely to encompass the true population value for that parameter.
What is the definition of a confidence level?
Probability that the confidence interval encompasses the true population value.
What is the confidence level set at?
95%
How is confidence interval estimated?
Calculated from the sample estimates.
What does a p value of <0.05 mean?
Reject the null hypothesis.
What are the 2 values in confidence levels known as?
Lower Limit
Upper Limit
What happens when the confidence level does NOT include 1?
Relative risk is significantly lower.
What is the Z score?
Describes how many standard deviations an individual value or sample mean is from the population mean.
