What is sensitivity?
Proportion of patients with the disease who have a positive test result
What is positive predictive value?
The chance that the patient has the condition if the diagnostic test is positive
What is negative predictive value?
The chance that the patient does not have the condition if the diagnostic test is negative
What is specificity?
Proportion of people without disease who also tested negative
NNT
The number of people requiring treatment to reduce outcomes by 1.
1/absolute risk reduction
How do you calculate absolute risk reduction?
ARR = EER -CER
EER Experimental event rate = Number of people with outcome who had intervention/total number given intervention.
CER control event rate = number with outcome with control/ total number with control.
What is the Wilcoxon signed rank test?
Comparing before & after results in same population group
For non-parametric data (not measurabel0
What is mann-whitney-u test?
Compares ratio/ordinal/interval scales of UNPAIRED data
What is chi-squared test?
Compare proportions or percentages e.g. compares the percentage of patients who improved following two different interventions
How do you calculate odds ratio?
e.g if 30 golfers and 30 non-golfers are assessed for golfers elbows.
- calculate odds for golfers e.g. 30 golfers get golfers elbow. Odds = 30/30 = 1
- Calculate risk for golfers. 30/60 = 0.5
- Calculate odds for non golfers = 10/50 = 0.2
- Calculate risk for non-golfers = 10/60 = 0.16
Odds ration therefore = 1/0.2 = 5
Odds = event happens/event doesn’t happen.
How do you calculate the likelihood ratio of a positive test?
sensitivity/1-specificity.
